Control apparatus of internal combustion engine

ABSTRACT

At a time of stopping an internal combustion engine, inertia energy of the engine is kept constant, for example, by controlling a number of engine revolution constant, while controlling combustion of the engine. By utilizing the controlled inertia energy, the engine is stopped at a predetermined crank angle position. Since the engine is stopped at the predetermined crank angle position by utilizing the controlled inertia energy, a large amount of energy for controlling the stop position of the energy is not needed, and the energy needed for the stop control can be reduced. Since the inertia energy utilized for the stop control is always controlled in a predetermined state, the engine can be stopped at a proper position reliably each time.

TECHNICAL FIELD

The present invention relates to a control apparatus of an internalcombustion engine. Particularly, the present invention relates to a stopand start control for stopping the internal combustion engine at aposition at which energy needed at the time of starting is the smallest,and at the same time, for executing early start of the engine byigniting fuel introduced and sealed in a specific cylinder at the timeof starting.

BACKGROUND ART

Recently, there is known an engine stop and start control apparatus forautomatically stopping an internal combustion engine (hereinafter, alsoreferred to as “engine”) when the vehicle stops and for automaticallyrestarting the engine to start the vehicle when an instruction to startis given in the stopped state, in order to reduce a fuel consumptionamount and exhaust gas during idling, from the viewpoint ofenvironmental conservation, resources and energy saving or the like.This control is also called “idling stop” or the like.

It is known that, when the idling stop is automatically carried out, itis effective to control the stop position of the engine in order tominimize required energy at the time of starting the engine. Minimizingthe required energy at the time of starting the engine brings about theadvantages that an engine starting device used after idling stop such asa motor generator (MG) can be miniaturized, and the useful life of abattery can be elongated by reducing the electric energy.

As a method for controlling the stop position of the engine, there areproposed methods for executing fuel cut when a specific cylinder comesto a position of a predetermined crank angle, and for stopping theengine at a predetermined position by setting a predicted value of acompression torque at the time of stopping the engine and by producing acounter torque equivalent to the predicted compression torque toestablish a balance.

Also, there is proposed an engine start apparatus in which the starteris rotated in a normal direction after the engine stop, and if the crankangle is at the crank angle stop position at which the starting torqueof a starter becomes large, the crankshaft is rotated in a reversedirection to a crank angle stop position at which a starting torquebecomes small before the next engine start, thereby improving thestarting performance at the time of starting the engine. This method isdisclosed in the Japanese Patent Application Laid-Open under No.2000-283010.

Further, there is known the engine start apparatus for executing thenext engine start by combusting the fuel in the cylinder supplied duringthe expansion stroke at the time of the engine stop. This method isdisclosed in the Japanese Patent Application Laid-Open under No.2002-4985.

However, in the method for executing the fuel cut at the predeterminedcrank angle for the specific cylinder in order to stop the engine at thepredetermined position, since the states of engine loads of auxiliarymachines and the like at the time of executing the fuel cut and thenumber of engine revolution immediately before the fuel cut are notalways constant, the falling manner of the number of the enginerevolution after executing the fuel cut until actual stopping of theengine may vary. No matter how small it may be, such a variation finallybrings about a large accumulated difference. Consequently, it ispractically difficult that the engine stop position is always controlledin a constant manner.

In the method for controlling the engine stop position by utilizing thebalance with the compression torque at the time of stopping the engine,first, it is difficult to accurately predict the value of thecompression torque. This is because the value of the compression torqueis affected by an air amount leaking out via a piston ring and is variedby the speed of the vehicle. Further, a large motor is needed because alarge torque has to be produced in order to balance with the compressiontorque, and hence the power consumption becomes large.

In the method for moving the crank angle to the position at which thestarting torque becomes small by utilizing the motor after stopping theengine, since a large torque is needed to rotate the crankshaft afterstopping the engine, a large motor is needed, after all.

On the other hand, as to the start control of the engine, by controllingthe engine stop position, the necessary torque at the time of startingcan be small and a motor for the engine start used at the time of idlingstop can be miniaturized, as explained above. However, as the motor forstarting is miniaturized, the possible output torque becomes small. As aresult, there occurs a problem that the time until the completion of thefirst explosion of the engine becomes long.

Also, when the motor for starting is miniaturized, falling of the torquewhen the number of engine revolution increases becomes large. This isespecially remarkable in a low voltage battery about 12V. Therefore,even if a piston of the cylinder in the compression stroke can get overthe first compression stroke top dead center by the motoring by thestarter motor, the piston may not get over the next compression stroketop dead center because enough inertia energy of the engine cannot begenerated due to the decreasing outputting torque of the starter motorwhen the number of engine revolution increases. In the worst case, themotor may lock around the top dead center.

Further, there may also occur a problem that the time until thecompletion of the first explosion becomes long because it takesconsiderable time to determine the cylinder when the number of enginerevolution is low.

DISCLOSURE OF THE INVENTION

The present invention is contrived in view of the above-describedproblems, and its object is to provide a control apparatus of aninternal combustion engine capable of accurately stopping the engine ata predetermined stop position with small energy. Another object of thepresent invention is to provide a control apparatus of an internalcombustion engine for realizing early ignition start of the internalcombustion engine.

According to one aspect of the present invention, there is provided acontrol apparatus of an internal combustion engine including: acombustion control unit which controls combustion of the engine at atime of stopping the engine; an inertia energy control unit whichcontrols inertia energy of the engine to be in a predetermined state;and a stop control unit which stops the engine at a predetermined crankangle position by utilizing the inertia energy.

The above-described control apparatus controls the combustion of theengine and controls the inertia energy of the engine to be in apredetermined state at the time of stopping the internal combustionengine. By utilizing the inertia energy thus controlled, the engine isstopped at a predetermined crank angle position.

Since the engine is stopped at the predetermined crank angle position byutilizing the controlled inertia energy, large energy is not needed tocontrol the stop position of the energy, and the energy needed for thestop control can be reduced. Also, since the inertia energy utilized forthe stop control is constantly controlled in a predetermined state, itis possible to stably stop the engine at the appropriate position eachtime.

The inertia energy control unit may control a number of enginerevolution to be within a range of a predetermined number of enginerevolution. The inertia energy of the engine is generally associatedwith the number of engine revolution, and the inertia energy of theengine can be controlled by controlling the number of engine revolution.Therefore, by controlling the number of engine revolution to be within apredetermined range, the inertia energy of the engine can be accuratelycontrolled.

The inertia energy control unit may control the inertia energy by amotor for driving the engine. Therefore, by utilizing the motorinstalled in the vehicle, the inertia energy can be controlled. Forexample, a motor generator for applying the driving force to therotational axis of the engine is provided on a so-calledeconomic-running vehicle having an idling stop function or a hybridvehicle. By using the motor generator, the inertia energy can becontrolled.

The combustion control unit may start the combustion of the engine whiledriving by the motor is continued, when a starting request occurs in theengine in a condition that the number of engine revolution is controlledto be within the predetermined number of engine revolution by the motor.While the motor controls the number of the engine revolution during anautomatic engine stop control for the purpose of the idling stop, if therequest for starting the engine, e.g., the start command of the vehicle,is issued, the combustion of the engine can be restarted to start theengine with continuing the driving by the motor. Therefore, the enginecan be quickly restarted when the start request is issued, even duringthe stop control.

The stop control unit may stop the engine at the predetermined crankangle position by adding control force to the engine by the motor fordriving the engine. At the time of stopping the engine at thepredetermined crank angle position by using the inertia energy, byadding the driving (assisting) force or braking force by the motor, ifnecessary, the accuracy of the stop position control can be improved.

The stop control unit may add the control force to the engine by themotor for driving the engine when the engine is not estimated to stop atthe predetermined crank angle position. Thereby, when it is estimatedthat the engine cannot be stopped at the predetermined crank angleposition by the inertia energy controlled to be the predetermined state,the engine can be controlled to stop at the predetermined crank angleposition by adding the control force by the motor.

The control apparatus of the internal combustion engine may furtherinclude a detecting unit which detects a number of idling revolution ofthe engine, and the stop control unit may inhibit stopping the enginewhen the number of idling revolution is larger than a predeterminedvalue. If the number of idling revolution is higher than a predeterminevalue at the time of stopping the engine, the load of the motor tocontrol the inertia energy becomes larger and the control becomesunstable. Therefore, by inhibiting the engine stop, the failure of thestop control is avoided.

The control apparatus of the internal combustion engine may furtherinclude a detecting unit which detects the number of idling revolution,and the combustion control unit may increase the combustion of theengine to increase the number of engine revolution before stopping thecombustion of the engine when the number of idling revolution is smallerthan the predetermined value. If the number of idling revolution islower than a predetermined value, appropriate inertia energy cannot beobtained and the stop control may fail. Therefore, the engine is stoppedby the inertia energy after the number of revolution is increased byincreasing the combustion.

The combustion control unit may stop the combustion of the engine whenthe inertia energy control unit controls the number of engine revolutionto be within the predetermined number of engine revolution. When thenumber of engine revolution is controlled by the motor, if thecombustion in the engine is continued, the number of revolution isvarieddue to the combustion and it becomes difficult for the motor tostably control the number of revolution. Therefore, it is preferred tocontrol the inertia energy in such a state that the combustion in theengine is stopped.

The control apparatus of the internal combustion engine may furtherinclude a unit for reducing loads of the engine when the stop controlunit performs an engine stop control. When the stop control of theengine is performed, if there is a load, e.g., the air conditioner, onthe engine, the energy necessary to control the revolution number of theengine becomes large, and the control may be unstable due to thevariation of the load. Therefore, it is preferred that the stop controlis performed with reducing the load on the engine as small as possible.

The control apparatus of an internal combustion engine may furtherinclude: a start control unit which drives the engine by the motor at atime of engine start; an estimation unit which estimates a cylinder in acompression stroke and/or an expansion stroke at the time of the enginestop; a detection unit which detects the cylinder; a supplying unitwhich supplies fuel to the cylinder; and a combustion unit whichcombusts the fuel supplied to the cylinder at the time of the enginestart.

In this control apparatus, the engine can be stopped at a predeterminedcrank angle position at the time of the engine stop. Therefore, theengine can be stopped at the crank angle position at which starting theengine is easy.

Furthermore, the control apparatus can estimate the cylinders in thecompression stroke and/or an expansion stroke at the time of the enginestop, and detect the cylinders. Thus, based on the detected result, atan optimal timing during executing the stop control, fuel can besupplied into the cylinder. At this time, since the mixture introducedinto the cylinder is well atomized and homogenized by receiving heatenergy from the cylinder, the mixture is easy to ignite.

Therefore, at the time of the engine start, by igniting the fuelintroduced in the compression stroke cylinder and/or the expansionstroke cylinder by an igniter, the fuel can be ignited and the enginecan be started. Thereby, the time until the first explosion can beshortened, and prompt engine start can be achieved. Since the enginedriving by the motor, i.e., cranking, is executed at the same time, itbecomes easy to get over the first and second compression stroke topdead centers to reliably execute the engine start.

If a vehicle is so-called “economic-running” vehicle to which idlingstop technique is applied, hybrid vehicles and the like, a waiting timefor the engine start can be shortened. In this case, the vehicle iscapable of promptly starting the engine because the cranking is executedby the motor (e.g., a motor generator and the like) while the ignitionis performed to the cylinder when requested to start the engine afterthe idling stop.

If the cranking by the motor is executed after the engine startsrevolution by the ignition start, the torque needed for the motor at thetime of the engine start can be small. Thus, the energizing time to themotor can be shortened, and a power consumption of a power supply unit(battery and the like) can be reduced.

In an example, the supplying unit supplies the fuel to the cylinder viaan intake port, or directly supplies the fuel to the cylinder.

According to this example, when the supplying unit executes fuel supplyvia the intake port, immediately before the engine stop control, thefuel can be supplied into the cylinder via the fuel injection apparatuswhen the cylinder is in the intake stroke. On the other hand, when thesupplying unit supplies the fuel directly into the cylinder, the fuelcan be supplied into the cylinder via the fuel injection apparatus atany one of the timings, i.e., during executing the engine stop control,at the time of the engine stop, and at the time of the engine start.

The predetermined crank angle position may be a stop position at which atorque of the motor needed at the time of the engine start becomessmall.

In this case, the engine can be stopped at the crank angle position atwhich the torque of the motor needed at the engine start is small. Thepredetermined crank angle may be 90° CA to 120° CA, for example.

The engine may stop at the predetermined crank angle position by themotor which controls a number of engine revolution to be within apredetermined number of engine revolution.

In this case, by transmitting the revolution driving force from themotor to the engine when the engine is in the predetermined number ofengine revolution, the number of engine revolution can be controlled tobe within the predetermined number of engine revolution. Thereby, theengine can be stopped at the predetermined crank angle position bykeeping the inertia energy included in the engine constant afterward.

The supplying unit may supply the fuel to the cylinder when the cylinderwhich is detected based on the detection unit immediately before thetime of the engine stop is in the intake stroke.

At the time of the engine stop, the cylinder can be estimated anddetected, and immediately before the engine stop control, the fuel canbe supplied into the cylinder via the fuel injection apparatus connectedto the intake port when the cylinder becomes in the intake stroke.

The start control unit may start the engine by driving the motor when acurrent value added to the motor is larger than a predetermined value atthe time of the engine start.

When a current value supplied to the motor is out of a predeterminedrange, it is highly possible that the torque of the motor needed at thetime of the engine start is not enough. Therefore, if the driving of themotor is executed for the engine start at this time, the motor may belocked. To the contrary, when the current value supplied to the motor iswithin the predetermined range, the torque of the motor needed for theengine start is kept enough. Thus, by driving the motor at this time,the lock of the motor can be prevented, and the cranking by the motorcan be reliably executed. Therefore, the engine start can be promptlyand reliably executed if the cranking by the motor is executed when themotor can be supplied with sufficient exciting current, in addition tothe ignition start to the expansion stroke cylinder and/or thecompression stroke cylinder, at the time of the engine start.

In a preferred example, the estimation unit may estimate the cylinderwhich is in the compression stroke and/or the expansion stroke, based onthe number of engine revolution at a time of stopping driving by themotor. In another preferred example, the estimation unit may estimatethe cylinder which is in the compression stroke and/or the expansionstroke, based on the number of engine revolution at the time of stoppingdriving by the motor and a kind of the stroke of each cylinder at a timeof starting driving by the motor. In that case, the estimation unit mayspecify the kind of the stroke of each cylinder, based on a cam positionof the cylinder.

The nature, utility, and further features of this invention will be moreclearly apparent from the following detailed description with respect topreferred embodiment of the invention when read in conjunction with theaccompanying drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system configuration of a vehicle, which performs anengine stop control according to the present invention;

FIG. 2 shows a schematic block diagram of an engine according to thepresent invention;

FIG. 3 is a view showing a configuration of a crank angle sensor and acam angle sensor;

FIGS. 4A to 4D show output signal waveforms of the crank angle sensorand the cam angle sensor;

FIG. 5 is a graph showing a transition of a number of engine revolutionduring an engine stop control;

FIG. 6 is a graph showing a state of a change of a crank angle positionduring an engine stop control;

FIG. 7 shows a flow chart of an engine stop control according to a firstembodiment;

FIG. 8 shows a flow chart of an engine stop control according to thefirst application example of the first embodiment;

FIG. 9 shows a flow chart of another engine stop control according tothe first application example of the first embodiment;

FIG. 10 shows a flow chart of an engine stop control according to thethird application example of the first embodiment;

FIG. 11 shows a flow chart of an engine stop control according to theforth application example according to the first embodiment;

FIG. 12 is a graph showing a transition of a number of engine revolutionduring an engine stop control according to the second embodiment;

FIG. 13 shows a flow chart of an engine stop control according to thesecond embodiment;

FIG. 14 shows a flow chart of an engine stop control according to thethird embodiment;

FIG. 15 shows an example of engine stop control according to a fourthembodiment of the present invention;

FIG. 16 shows an example of engine start control according to the fourthembodiment of the present invention;

FIG. 17 is a flow chart of an engine stop control according to thefourth embodiment;

FIG. 18 is a flow chart of an engine start control according to thefourth embodiment;

FIG. 19 shows an example of engine stop control according to a fifthembodiment of the present invention;

FIG. 20 shows an example of engine start control according to the fifthembodiment of the present invention;

FIG. 21 is a flow chart of an engine stop control according to the fifthembodiment;

FIG. 22 is a flow chart of an engine start control according to thefifth embodiment; and

FIG. 23 is a flow chart of an engine start control according to a sixthembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be explained belowwith reference to the attached drawings.

[Configuration of Vehicle]

First, the description will be given of a schematic configuration of avehicle to which a control apparatus of an internal combustion engineaccording to the present invention is applied. A control apparatus ofthe internal combustion engine according to the present invention isintended for so-called “economic-running” vehicles, hybrid vehicles andthe like to which idling stop technique is applied. “An economic-runningvehicle” is a vehicle which is equipped with an electric motor (motorgenerator) mainly for the purpose of starting the engine and whichautomatically restarts the engine by the motor generator after stoppingthe engine by the idling stop control. “A hybrid vehicle” is a powertrain using an engine and a motor generator as power sources. In ahybrid vehicle, both the engine and the motor generator work incombination in accordance with a running state, or are separately used,and power performance which is smooth and excellent in response can beobtained.

FIG. 1 shows a system configuration of a vehicle 10 according to thepresent invention.

As shown in FIG. 1, the vehicle 10 includes a DC starter 1, an engine 2,a motor generator 3 which generates electricity by a driving forceoutputted from the engine 2 and is drivable as a cell motor on theoccasion of starting the engine 2, a motor control unit 4 to control themotor generator 3 and the like, a power supply unit 5 for exchangingelectric power with the motor generator 3 and the like via the motorcontrol unit 4, a power supply cable 6 for connecting the motorgenerator 3, the motor control unit 4 and the power supply unit 5,respectively, a power transmission system 7 for transmitting a drivingforce generated from the engine 2 to wheels, and the wheels 8.

Next, each of the above-described units will be explained with referenceto FIG. 1.

The DC starter 1 is a dc-type cell motor for starting the engine 2. TheDC starter 1 has a shaft, receives a power supply from a 12V powersupply unit when an ignition switch is turned to an ON state, androtates the shaft. By the rotation of the shaft of the DC starter 1, acrankshaft of the engine 2 is rotated and the engine 2 is started.Specifically, a pinion gear is mounted on a tip end portion of the shaftof the DC starter 1. The pinion gear is meshed with a ring gear of aflywheel provided at the crankshaft of the engine 2. Consequently, whenthe DC starter 1 receives a power supply from the 12V power supply unitby the start of the engine 2, the pinion gear is meshed with the ringgear of the flywheel and rotated to rotate the flywheel. As a result,the crankshaft with a predetermined number of pistons being connected isrotated, and therefore the engine 2 can be started by the rotationaldriving force. Driving the crankshaft to start the engine is called“cranking”.

The engine 2 is the internal combustion engine for generating power byexploding air-fuel mixtures (herein after simply referred to as“mixture”) in cylinders. There are gasoline engines with gasoline as afuel, diesel engines with light oil and the like as a fuel, and the likeas the internal combustion engines. As the gasoline engines, there arefour-cycle gasoline engines which complete one cycle of intake,compression, expansion and exhaust during two rotations of crankshaft togenerate power, and two-cycle gasoline engines which complete theaforementioned one cycle during one rotation of crankshaft. The vehicle10 in this embodiment is assumed to be the four-cycle gasoline engine.

FIG. 2 shows one example of a schematic configuration of the engine 2.

An intake port 24 formed at a cylinder head 12 is opened and closed byan intake valve 26. Intake air is supplied into the intake port 24 viaan intake passage 28. The intake passage 28 is provided with a surgetank 30, and a throttle valve 32 is provided at an upstream of the surgetank 30. An opening (throttle opening TA) of the throttle valve 32 isadjusted by an electric motor 34, and the throttle opening TA isdetected by a throttle opening sensor 36.

The engine 2 is a so-called port-injection type engine, and the intakeport 24 is provided with a fuel injection valve 14. An air-fuel mixtureis generated by the intake air inside the intake port 24 and the fuelinjected into the intake port 24, and is introduced into thecombustion-chamber 20 partitioned by the cylinder block 16, the piston18 and the cylinder head 12. The ignition plug 22 is disposed at aceiling portion of the combustion chamber 20, and ignites the mixtureintroduced from the intake port 24. High pressure fuel is supplied tothe fuel injection valve 14 from a high pressure fuel pump (not shown)via a delivery pipe 14 a. This enables the injection of fuel into thecombustion chamber 20 from the fuel injection valve 14 even in the lastperiod of the compression stroke. Fuel pressure in the delivery pipe 14a is detected by the fuel pressure sensor 14 b.

The exhaust port 38 formed at the cylinder head 12 is opened and closedby the exhaust valve 40. Exhaust gas discharged to the exhaust port 38from the combustion chamber 20 is discharged to the outside via theexhaust passage 42, an exhaust gas purifying catalyst (not shown) andthe like.

Reciprocal movement of the piston 18 generated by the combustion of themixture inside the combustion chamber 20 is converted into rotationalmovement of the crankshaft 46 via the connecting rod 44. The crankshaft46 transmits power to the wheels 8 via a torque converter and atransmission not shown.

Apart from such a power transmission system, one end of the crankshaft46 is connected to the pulley 50 (hereinafter, also called “crankshaftpulley”) via the electromagnetic clutch 48. The pulley 50 is capable oftransmitting power to and from other three pulleys 54, 56 and 58 by thebelt 52. In this example, the compressor 60 for an air conditioner ismade drivable by the pulley 54, and the power steering pump 62 is madedrivable by the pulley 56. The other pulley 58 (hereinafter, also called“MG pulley”) is connected to the motor generator 3. The motor generator3 has a function as a generator for generating power by the enginedriving force from the side of the MG pulley 58, and a function as amotor for supplying the driving force of the motor generator 3 to theside of the MG pulley 58.

An ECU 70 (Engine Control Unit) mainly constructed with a microcomputerincludes an input-output device, a storage device, a central processingunit and the like, and supervises and controls the whole system of thevehicle 10. The ECU 70 controls the vehicle 10 to be in an optimalcondition based on input information from each sensor and the likeprovided on the engine 2. Specifically, the ECU 70 detects the fuelpressure from the aforementioned fuel pressure sensor 14 b, the throttleopening TA from the throttle opening sensor 36, a revolving number ofmotor generator from a rotational frequency sensor included in the motorgenerator 3, the voltage of the power supply unit 5 or the currentamount of the power supply unit 5 at the time of charge and discharge, aswitching state of the ignition switch 72, a vehicle speed SPD from thevehicle speed sensor 74, a stamping or depressing amount on anaccelerator pedal (accelerator opening ACCP) from the acceleratoropening sensor 76, presence or absence of stamping on a brake pedal fromthe brake switch 78, a number of revolution of the crankshaft 46 (i.e.,number of engine revolution NE) from an engine revolution number sensor80, an intake air amount GA from the air flow meter 82, the enginecooling water temperature THW from the cooling water temperature sensor84, presence or absence of stamping on the accelerator pedal from theidle switch 86, an air fuel ratio detection value Vox from the air fuelratio sensor 88 provided in the exhaust passage 42, a rotation positionof a camshaft from the cam angle sensor 92, and a rotation angle (crankangle) of the crankshaft from the crank angle sensor 90, respectively.

Based on the data thus obtained, the ECU 70 drives the electric motor 34to adjust the throttle opening TA, and adjusts the injection timing ofthe fuel by the fuel injection valve 14. Further, when an automatic stopcondition is established, the ECU 70 controls the fuel injection fromthe fuel injection valve 14 to automatically stop the operation of theengine 2. When an automatic start condition is established, the ECU 70controls the rotation the crankshaft 46 by the driving force of themotor generator 3 transferred via the pulley 58, the belt 52, the pulley50 and the electromagnetic clutch 48 to start the engine 2. Further, theECU 70 executes an ignition timing control, and the other necessarycontrols.

The output signal of the crank angle sensor 90 is inputted to the ECU70. The crank angle sensor 90 is a magnetic type sensor or the likecapable of detecting an object to be detected (for example, metal andthe like), and is provided at a predetermined position near thecrankshaft 46 in the engine 2. Namely, a gear with projections anddepressions being formed on an outer circumference (hereinafter, called“signal rotor”) is attached at a predetermined position on thecrankshaft 46, and the crank angle sensor 90 is provided at anappropriate position to detect the number of teeth of the signal rotor.The crank angle sensor 90 can detect the rotation angle of thecrankshaft 46 (hereinafter, called “crank angle”) with resolution of,for example, about 10° to 30° CA. When the crankshaft 46 is rotated, thesignal rotor also rotates in synchronization with the crankshaft 46. Inthis situation, the crank angle sensor 90 detects the number of teeth ofthe signal rotor and outputs it to the ECU 70 and the like as a pulsesignal. The ECU 70 counts the pulse signal outputted from the crankangle sensor 90, and converts it into a crank angle. Thus, the ECU 70and the like detect the crank angle. The crank angle sensor 90 isdirectly provided in the engine 2, and therefore it can detect the crankangle as an absolute angle.

The crank angle sensor 90 outputs one pulse signal to the ECU 70 and thelike when it detects one of teeth of the signal rotor. Consequently, thepulse signal outputted from the crank angle sensor 90 is in the sameoutput state irrespective of whether the crankshaft 46 is rotated in anormal direction or a reverse direction, and therefore the ECU 70 andthe like cannot detect whether the rotation of the crankshaft 46 is inthe normal direction or in the reverse direction.

The motor generator 3 is connected to the crankshaft 46 through thepulley 50, the pulley 58 and the belt 52. One of the crankshaft pulley50 connected to the crankshaft 46 and the MG pulley 58 connected to themotor generator 3 is rotationally driven, whereby power is transmittedto the other via the belt 52.

The motor generator 3 has the function as the motor (electric motor)rotationally driving by receiving power supply from the power supplyunit 5 which will be described later, and has the function as thegenerator (electric generator) for generating electromotive forces atboth ends of a three-phase coil when the motor generator 3 is rotated byreceiving the rotational driving force from the wheels 8. When the motorgenerator 3 functions as the electric motor, the motor generator 3rotates by receiving the electric power supply from the power supplyunit 5, and transmits the rotational driving force to the crankshaftpulley 50 to rotate the crankshaft 46 to start the engine 2. On theother hand, when the motor generator 3 functions as the electricgenerator, the rotational driving force from the wheels 8 is transmittedto the MG pulley 58 at the side of the motor generator via thecrankshaft 46 and the crankshaft pulley 50 to rotate the motor generator3. When the motor generator 3 is rotated, an electromotive force isgenerated in the motor generator 3, and the electromotive force isconverted into a direct current via the motor control unit 4 to supplyelectric power to the power supply unit 5. Thus, the power supply unit 5is charged.

Returning to FIG. 1, a motor angle sensor 3 a, in which a Hall elementor the like is preferably applied to a detection portion, is provided ata predetermined position in the motor generator 3. The motor anglesensor 3 a can detect the rotation angle of the shaft of the motorgenerator 3 with high resolution of substantially 7.5° CA unit. When themotor generator 3 is rotationally driven by receiving the supply ofelectric power from the power supply unit 5, the motor angle sensor 3 adetects the rotation angle of the shaft. Specifically, the motor anglesensor 3 a is provided at each of phases U, V and W so as to be able todetect an alternating current of each of the U, V and W phases. Each ofthe motor angle sensors 3 a detects an alternating current of each ofthe U, V and W phases and converts it into a pulse signal, and outputsit to the motor control unit 4.

The motor control unit 4 is provided in the engine 2, and connected tothe motor generator 3 and the power supply unit 5 by the power supplycable 6, respectively. The motor control unit 4 is mainly constructed byan inverter, a converter, a controlling computer or the like.

The inverter converts a high voltage direct current from the powersupply unit 5 into a predetermined three-phase alternating current tosupply electric power to the motor generator 3. On the other hand, theinverter converts an electromotive force (three-phase alternatingcurrent) generated from the motor generator 3 into a direct currentsuitable for charging the power supply unit 5.

The converter is a DC/DC converting device for converting apredetermined DC voltage into another predetermined DC voltage. Namely,the converter drops the rated voltage (for example, 36 V voltage) of thepower supply unit 5 to a predetermined voltage (for example, 12Vvoltage) to drive auxiliary machines and the like, or charges a 12Vpower supply unit loaded on the vehicle.

The controlling computer controls the inverter and the converter.Namely, the controlling computer controls the driving torque and powergeneration amount of the motor generator 3 in the optimal state, andcontrols the charge amount to the power supply unit 5 in the optimalstate to perform charging. Specifically, when the motor generator 3functions as the electric motor, the controlling computer controls thedriving torque and the power generation amount of the motor generator 3based on the electric power supplied from the power supply unit 5. As aresult, the motor generator 3 is controlled in the optimal state tofunction as the electric motor. On the other hand, when the motorgenerator 3 functions as the electric generator, the controllingcomputer supplies a predetermined direct current to the power supplyunit 5 based on the electromotive force generated from the motorgenerator 3 to charge the power supply unit 5.

The motor control unit 4 counts the number of pulse signals outputtedfrom the aforementioned motor angle sensor 3 a, and thereby converts thenumber into the rotation angle of the shaft of the motor generator 3.The motor control unit 4 converts the converted rotation angle of theshaft into the crank angle based on the rotation ratio of the crankshaftpulley 50 and the MG pulley 58. As a result, the motor control unit 4can detect the crank angle with high resolution of substantially 3° CAunit.

The motor control unit 4 can detect whether the shaft of the motorgenerator 3 rotates in the normal or in the reverse direction. Namely,the output state of the pulse signal of each of the phases U, V and Wdiffers when the shaft of the motor generator 3 rotates in the normaldirection and in the reverse direction. The pulse signal of each of thephases U, V and W when the shaft of the motor generator 3 rotates in thenormal direction is in such an output state according to the phasedifference as the pulse signal of the U phase is firstly outputted for apredetermined time, thereafter, the pulse signal of the V phase isoutputted for a predetermined time later, thereafter, the pulse signalof the W phase is outputted for a predetermined time later, and they arerepeated periodically. In contrast, the pulse signal of each of thephases U, V and W when the shaft of the motor generator 3 rotates in thereverse direction is in such an output state as the pulse signalopposite to that of the normal rotation. Namely, when the shaft of themotor generator 3 rotates in the reverse direction, each of the pulsesignals for the predetermined time is periodically repeated in the orderof the W phase, V phase and U phase. For this reason, the motor controlunit 4 can detect whether the shaft of the motor generator 3 rotates inthe normal or the reverse direction, based on the phase differencebetween them.

The power supply unit 5 is a secondary battery such as a lead battery ora nickel hydrogen battery. The power supply unit 5 is placed at, forexample, a rear part of the vehicle 10 to increase space efficiency ofthe vehicle 10. The power supply unit 5 may have a rated voltage of 36V,for example. The power supply unit 5 has high input-outputcharacteristics at the time of actuation of the motor generator 3 or inenergy regeneration during braking the vehicle. Specifically, the powersupply unit 5 supplies electric power to the auxiliary machines, themotor generator 3 and the like. Electric power supply to the motorgenerator 3 is mainly performed while the vehicle 10 is stopped. Whenthe vehicle 10 is running or braking, the electromotive force generatedfrom the motor generator 3 is converted into a direct current via themotor control unit 4 and supplied to the power supply unit 5. As aresult, the power supply unit 5 can be charged.

The power supply cable 6 is connected between the motor generator 3 andthe motor control unit 4, and also between the motor control unit 4 andthe power supply unit 5 as described above, and plays the part ofpassing the direct current and the three-phase alternating current.

The power transmission system 7 is mainly constructed by the torqueconverter, a lock-up clutch, a transmission, a power switching mechanismand the like. As a result of their cooperation, the power transmissionsystem 7 transmits or shuts off the rotational driving force generatedfrom the engine 2 or the motor generator 3 to or from the wheels 8 inaccordance with the running state. Also, the power transmission system 7transmits the rotational driving force from the wheels 8 to the motorgenerator 3 at the time of braking and the like.

The wheel 8 includes tires and the like for transmitting the rotationaldriving force from the power transmission system 7 to a road surface. Inthis embodiment, rear wheels are shown as the wheels 8.

Next, examples of the crank angle sensor 90 and the cam angle sensor 92will be explained.

As shown in FIG. 3, a signal rotor 91 (omitted in FIG. 2) is attached tothe crank shaft 46. On the outer circumferential portion of the signalrotor 91, 34 teeth (projection portions) 91 a formed at equal angles(here, spaced by 10°) with an axis of the crankshaft 46 as a center anda wide lacked tooth (portion with no teeth existing) 91 b are provided.The length of the lacked tooth portion 91 b corresponds to that of twoteeth 91 a. The crank angle sensor 90 is provided to oppose the outercircumferential portion of the signal rotor 91. When the crankshaft 46is rotated, the teeth 91 a and the lacked tooth 91 b of the signal rotor91 pass near the crank angle sensor 90 in sequence, whereby a rotationsignal of pulse form (hereinafter, called “NE signal”) including pulsescorresponding to the number of passages of the teeth 91 a and the lackedtooth 91 b is outputted from the crank angle sensor 90.

On the other hand, three projections 27 a, 27 b and 27 c are provided onthe outer circumferential surface of the intake camshaft 27 to bearranged at spaces of 90° (corresponding to 180° CA) with an axis of theintake camshaft 27 as a center. Accordingly, a space between theprojection 27 a and the projection 27 c at both ends is 180°(corresponding to 360° CA). The cam angle sensor 92 for detecting theprojections 27 a to 27 c and outputting the detection signals isprovided to oppose these projections 27 a to 27 c. When the intakecamshaft 27 is rotated, the projections 27 a to 27 c pass near the camangle sensor 92. As a result, a detection signal in a pulse form isoutputted from the cam angle sensor 92 corresponding to each passage ofthe projections 27 a to 27 c.

Here, the signals obtained from the crank angle sensor 90 and the camangle sensor 92, which are inputted into the ECU 70 when the engine 2 isdriven, are shown in FIGS. 4A, 4B, 4C and 4D. FIG. 4A shows a voltagewaveform generated in the cam angle sensor 92 according to the rotationof the intake camshaft 27. FIG. 4B is the waveform obtained byconverting the voltage waveform of FIG. 4A into the cam angle signal (G2signal) in the pulse form. FIG. 4C shows a voltage waveform generated inthe crank angle sensor 90 according to the rotation of the crankshaft46. FIG. 4D is the voltage waveform obtained by converting the waveformof FIG. 4C into the NE signal. In this example, in the NE signal, thenumber of pulses corresponding to the teeth 91 a is 34 per one rotation(360° CA) of the crankshaft 46. Among the rotation signals outputtedfrom the crank angle sensor 90, in the portion corresponding to thelacked tooth 91 b, the space between the pulses is made wide due to theabsence of 2 pulses. The number of the portions with the wide pulsespace is one per one rotation (360° CA) of the crankshaft 46.

The ECU 70 detects rotation phases of the crankshaft 46 and the intakecamshaft 27 based on the NE signal from the crank angle sensor 90 andthe cam angle signal from the cam angle sensor 92. The ECU 70 performscylinder discrimination for each cylinder (#1 to #4) based on therotation phases of the crankshaft 46 and the intake camshaft 27, andselects the cylinder for which the fuel injection and the ignitionshould be performed from among the cylinders (#1 to #4).

[Operation of Vehicle]

Next, an operation of the vehicle 10 constituted as described above willbe explained. The vehicle 10 performs various kinds of operations inaccordance with various operation states such as stop, start, normalrunning, accelerative running, braking or the like.

The engine 2 is in a stopped state during automatic stop (idling stop)of the vehicle 10. When driving of auxiliary machines such as an aircompressor, a water pump, a power steering pump or the like is necessaryin this state, the motor generator 3 receives the electric power supplyfrom the power supply unit 5 and drives these auxiliary machines withoutdriving the engine 2. However, the engine 2 and the motor generator 3are rotatably connected with each other via the V belt and therespective pulleys. Therefore, when the shaft of the motor generator 3is rotated, the rotational driving force is transmitted to the engine 2in this state. Consequently, in order to drive only the above-describedauxiliary machines, the electromagnetic clutch is operated to shut offthe rotational driving force from the motor generator 3 so that thecrankshaft of the engine 2 is not rotated. This enables to drive onlythe auxiliary machines without driving the engine 2.

At the time of starting the vehicle 10, namely, when a driver takes hisor her foot off the brake pedal while the vehicle is in the idling stopstate, the motor generator 3 raises the number of revolution to thevicinity of the number of idling revolution. Then, when the driverstamps or depresses the accelerator pedal, the motor generator 3 rotatesthe crankshaft of the engine 2 and automatically restarts the engine 2.When a predetermined time elapses from the brake off operation, namely,from the time when the driver takes his or her foot off the brake pedal,the engine 2 may also be automatically restarted to obtain optimal powerperformance.

At the time of normal running, the vehicle 10 runs by the driving forcefrom the engine 2, which is transmitted to the wheels 8 as in theordinary vehicles. During normal traveling, if the voltage of the powersupply unit 5 is low, the driving force from the wheels 8 is transmittedto the motor generator 3 and the motor generator 3 performs electricpower generation. As a result, the motor generator 3 functions as anelectric generator, and charges the power supply unit 5 to replenishinsufficient electric power of the power supply unit 5 (hereinafter,this operation state will be called “regeneration”) Thereby, the powersupply unit 5 is always kept in a proper charged state.

When the vehicle 10 performs uphill running and accelerative running,the motor generator 3 is driven by using the electric power of the powersupply unit 5 in addition to the state during the aforementioned normalrunning, in order to provide proper power performance, and therotational driving force by the motor generator 3 may be given to therotational driving force of the engine 2 (hereinafter, this operationstate will be called “assist”). This allows the vehicle 10 to obtainhigh power performance with effective use of the two power sources,i.e., the engine 2 and the motor generator 3.

At the time of braking in deceleration and the like, the driving forceby the wheels 8 is transmitted to the motor generator 3 via the powertransmission system 7 and the engine 2, and the regeneration isperformed.

[Engine Control]

Next, an engine stop control of the vehicle 10 will be explained. Asdescribed above, the vehicle 10 performs idling stop, namely,automatically stops the engine 2 at the time the vehicle 10 stops.Thereafter, when the driver takes his or her foot off the brake pedal,the motor generator 3 raises its revolution close to the number ofidling revolution of the engine 2. Then, when the driver stamps ordepresses the accelerator pedal, the motor generator 3 is rotationallydriven, and the rotational driving force automatically restarts theengine 2. In this situation, in order to smoothly start running thevehicle 10 at the time of automatic start of the engine 2, the crankangle is controlled to stop at the optimal crank angle stop positioninside the engine 2 at the time of idling stop. In the followingexample, accurate stop control is performed by effectively utilizinginertia energy of the engine 2 at the time of stopping the vehicle.

1st Embodiment

A method for controlling the crank angle to the optimal crank angle stopposition will be described hereinafter. The optimal crank angle stopposition is assumed to be a stop position of the crank angle, whichmakes it easy to get over the top dead center of the compression strokeat the time of restarting the engine 2 in the cylinder at thecompression stroke. For example, in the case of the four-cylinder engineas in this example, the crank angle stop position is optimal if it iswithin a range of the crank angle of 90° CA to 120° CA.

In summary, in the ordinary stop control method of the vehicle 10, theECU 70 executes fuel cut to the engine 2 at a predetermined timing fromthe idling state, and automatically stops the engine 2 by the inertiaenergy which the engine 2 has thereafter. However, the inertia energywhich the engine 2 has varies each time according to the number ofengine revolution at the time of the fuel cut, and the crank angle stopposition differs each time accordingly. For this reason, with theordinary stop control method of the vehicle 10, it is difficult tocontrol the crank angle to stop at the optimal crank angle stopposition, and the next engine start load becomes large depending on thecrank angle stop position when the vehicle actually stops. Consequently,in relation with the output torque which the motor generator 3 has, thecrankshaft of the engine 2 cannot be rotated, and the probability offailure of automatic restart of the engine 2 becomes high.

Consequently, in this example, the number of engine revolution is keptconstant at a predetermined timing after the fuel cut, whereby theinertia energy which the engine 2 has is made constant at that point oftime. Thereafter, the inertia energy which the engine 2 has at thatpoint of time is utilized to stop the rotation of the engine 2. By this,the crank angle can be reliably controlled to stop at the optimal crankangle stop position every time.

Especially, in this embodiment, the motor generator 3 is used to makethe number of engine revolution constant. Namely, a rotational drivingforce from the motor generator 3 is given to the crankshaft at apredetermined timing after the fuel cut (hereinafter, called“motoring”), whereby the inertia energy which the engine 2 has is madeconstant. Thus, the crank angle at the time of stopping the engine iscontrolled to stop at the optimal crank angle stop position. When thecrank angle is at the optimal crank angle stop position, the enginestart load at the time of starting the engine can be minimized, and thefailure of automatic restart of the engine 2 can be effectivelyprevented.

The manner of controlling the number of engine revolution at the time ofstopping the engine with use of the motor generator 3 is shown in FIG.5. In FIG. 5, the waveform 100 represents the variation of number ofengine revolution according to the engine stop control of thisembodiment. The waveform 101 represents a fuel cut signal in the enginestop control, and the fuel cutis executed when the fuel cut signal is atan H-level. The waveform 102 represents a drive signal (MG drive signal)of the motor generator 3, and the motor generator 3 is driven during theperiod in which the MG drive signal is at the H-level.

If it is assumed that the driver takes his or her foot off theaccelerator pedal at time t0, the number of revolution of the engine 2after time t0 substantially becomes the number of idling revolution NE1.If it is assumed that the driver depresses the brake pedal at time t1,the ECU 70 sets the fuel cut signal to H-level at this point of time,and gives an instruction of the fuel cut. When the fuel cut is executedat time t1, the number of revolution of the engine 2 graduallydecreases. When the ECU 70 detects that the number of engine revolutiondecreases down to a predetermined motor setting number of revolution NE2(time t2), the ECU 70 sets the MG driving signal to the H-level, drivesthe motor generator 3, and drives the engine 2 by the motor generator 3.

The motor generator 3 drives the engine 2 at the predetermined motorsetting number of revolution NE2 for a predetermined period (time t2 tot3), and when the predetermined period elapses, the ECU 70 stops themotor generator 3 (time t3). When the driving force by the motorgenerator 3 is removed at time t3, the engine 2 is rotated only by theinertia energy which the engine 2 has at that point of time (i.e., timet3), and therefore the number of engine revolution gradually decreases,and the engine 2 stops in the vicinity of time t4.

In this manner, in the present embodiment, the driving of the engine 2is temporarily switched to the driving by the motor generator 3 at thetime of stopping the engine, and after the engine 2 is kept at thepredetermined number of revolution NE2, the driving force of the engineis removed. The inertia energy, which the engine 2 has at the point oftime when the driving force is removed, is mainly determined by thenumber of engine revolution at that point of time. Therefore, byremoving the driving force after the number of engine revolution is keptat the predetermined number of engine revolution NE2, the engine 2 hasthe same inertia energy each time, and stops in the same manner.

Next, a behavior of the engine until the engine stops after the drivingforce is removed at the predetermined number of engine revolution NE2 asdescribed above will be explained. FIG. 6 shows the displacement of thecrank angle of the engine 2 after the driving force for the engine 2 isremoved. In FIG. 6, the vertical axis shows the displacement of thecrank angle (° CA) of a predetermined cylinder. It is noted that the“predetermined cylinder” is the cylinder which is in the compressionstroke when the crank angle is displaced from 0° CA to 180° CA, forexample, the #3 cylinder. The horizontal axis shows time (second).

Specifically, the vertical axis shows the crank angle displacement (°CA) when the piston corresponding to the predetermined cylinder shiftsfrom the compression stroke to the expansion stroke, and shows the crankangle displacement at every 30° CA from the bottom dead center (0° CA)to the top dead center (180° CA). Meanwhile, the horizontal axis showsthe lapse of time (0.6 (second)) from the motoring stopping time (0(second)) until the crank angle of the predetermined cylinder iscontrolled to stop at the optimal crank angle stop position at every 0.1(second).

Next, the graphs in FIG. 6 will be explained. In FIG. 6, two kinds ofgraphs are shown. They are a graph 110 for the case in which the numberof engine revolution at the time of stopping driving (motoring) by themotor generator 3 is high and a graph 112 for the case in which it islow. Namely, during the time from 0 second to 0.1 seconds, the graph 110with a large gradient shows the crank angle displacement when the numberof engine revolution at the time of stopping motoring is high, and thegraph 112 with a small gradient shows the crank angle displacement whenthe number of engine revolution at the time of stopping motoring is low.

First, from 0 second to the vicinity of 0.1 second, it is shown that thepiston corresponding to the predetermined cylinder rises from the bottomdead center to the top dead center in the compression stroke. The pistoncorresponding to the center of the compression stroke just after 0.1second elapses. At this time, the crankshaft 46 of the engine 2 isrotating in the normal direction.

Thereafter, the piston corresponding to the predetermined cylindercannot get over the top dead center (180° CA) of the compression stroke,and the crankshaft of the engine 2 is rotated in the reverse directionuntil it is near 0.3 second. This is for the following reason. As aresult that the piston corresponding to the predetermined cylinderapproaches the top dead center of the compression stroke, the volumetriccapacity in the cylinder gradually becomes smaller, and the pressurebecomes higher. In proportion to this, the compression reaction force116 to push back the piston becomes larger in the cylinder. Accordingly,in the vicinity of the top dead center of the compression stroke, thecompression reaction force is the largest in the cylinder, and thereforethe inertia energy which the engine has at that point of time cannotbeat the compression reaction force. Thus, the piston corresponding tothe predetermined cylinder is pushed back to the side of the bottom deadcenter of the compression stroke. Thus, the piston corresponding to thepredetermined cylinder cannot get over the top dead center of thecompression stroke, and the crankshaft of the engine 2 is rotated in thereverse direction.

Thereafter, the piston corresponding to the predetermined cylinder movesto the bottom dead center of the compression stroke, and the crankshaft46 of the engine 2 is rotated in reverse again in the vicinity of 0.3second. Namely, the crankshaft of the engine 2 is rotated in the normaldirection. This is for the following reason. Namely, at this time, thepiston corresponding to the predetermined cylinder firstly descends tothe bottom dead center of the compression stroke. In the compressionstroke, the intake and exhaust valves are both in the closed state, andtherefore the volumetric capacity inside the cylinder becomes graduallylarger as the piton descends to the bottom dead center of thecompression stroke. Consequently, negative pressure is formed inside thecylinder, and the negative pressure becomes gradually larger.Accordingly, the piston corresponding to the predetermined cylinder isreturned in the direction of the top dead center again by a reactionforce 118 caused by the negative pressure. As a result, the crankshaftof the engine 2 is rotated in the normal direction again.

Thereafter, the inertia energy which the engine 2 has graduallydecreases from the vicinity of 0.3 second, and the engine 2 stops after0.6 second elapses. As a result, the crank angle stop position convergeswithin a range of the crank angle of 90° CA to 120° CA. If the crankangle stop position ultimately converges within the range of the crankangle of about 90° CA to 120° CA, it is considered that the crank angleis controlled to stop at the optimal crank angle stop position, and thestop control is successful.

As described above, the number of engine revolution at the time ofstopping the motoring is preset, in advance, within a suitable range, inwhich the engine indicates the above-described behavior after stoppingthe motoring. An upper limit of the suitable range for the number ofengine revolution is the number of engine revolution at which thepredetermined cylinder of the engine cannot get over the next top deadcenter by the inertia energy of the engine 2 at that number of enginerevolution. This is because the predetermined cylinder gets over thenext top dead center after stopping the motoring when the number ofengine revolution is higher than the suitable range at the time ofstopping the motoring, and does not stop at the optimal crank angle stopposition eventually, as shown in FIG. 6. On the other hand, a lowerlimit of the suitable range for the number of engine revolution is thenumber of engine revolution at which the crank angle, which is rotatedin the reverse direction by the compression reaction force 116, can beturned over again to the normal direction due to a reaction force 118 bythe negative pressure in the cylinder, in a case when the motoring isstopped at that number of engine revolution. If the number of enginerevolution at the time of stopping the motoring is lower than the lowerlimit of the number of engine revolution, the engine which rotates inthe reverse direction by the compression reaction force 116 cannot turnover again to the normal direction, and finally the engine cannot stopwithin the range of the optimal crank angle stop position.

As described above, it is understood that the crank angle stops at theoptimal crank angle stop position by the inertia energy of the engine 2,if the number of engine revolution is within the suitable range (e.g.,within the constant range of about 300 (rpm) to 500 (rpm)) when themotoring is ended. Thus, in the embodiment, the ECU 70 keeps the numberof engine revolution constant each time by executing the motoring at thepredetermined timing, after executing the fuel cut at the predeterminedtiming in the constant idling state (e.g., around 1400 (rpm)). Here, theexecution time of the motoring is the time for keeping the inertiaenergy of the engine 2 constant after stopping the motoring, i.e., thetime needed until the number of engine revolution by the motoringbecomes stable at the predetermined number of engine revolution NE2. Forexample, the execution time may be the time in which the crankshaft ofthe engine 2 rotates twice.

After stopping the motoring, the constant inertia energy of the engine 2is effectively utilized to stop the engine. Namely, the pistoncorresponding to the predetermined cylinder operated by the inertiaenergy of the engine 2 receives, first, the compression reaction force116 occurring at the top dead center of the compression stroke, andsecond, the reaction force (the reaction force by the negative pressure)118 occurring in the compression stroke. Thereby, the inertia energy ofthe engine 2 is effectively consumed, and the crank angle can becontrolled to be the optimal crank angle stop position.

It is noted that the compression reaction force 116, which is receivedby approach of the piston corresponding to the predetermined cylinder tothe top dead center of the compression stroke, becomes large, when thenumber of engine revolution after stopping the motoring is high withinthe suitable range, as understood from FIG. 6. However, the reactionforce 118 in the cylinder in the compression stroke by the negativepressure becomes small. Thereby, by operating those normal and reversereaction forces with each other, the inertia energy of the engine 2 canbe effectively absorbed.

On the other hand, when the number of engine revolution after stoppingthe motoring is low within the suitable range, the compression rotationforce 116, which is received by approach of the piston corresponding tothe predetermined cylinder to the top dead center of the compressionstroke, becomes small as understood from FIG. 6. However, the reactionforce 118 which brings the piston to the side of the top dead center bythe negative pressure becomes large. Thereby, by operating those normaland reverse reaction forces with each other, the inertia energy of theengine 2 can be effectively absorbed.

Namely, when the reaction force (compression reaction force) 116 whichis received first is large, the reaction force (reaction force occurringby the negative pressure) 118 which is received next is small. On theother hand, when the reaction force (compression reaction force) 116which is received first is small, the reaction force (reaction forceoccurring by the negative pressure) 118 which is received next is large.According to the embodiment, if the number of engine revolution afterstopping the motoring is within the suitable range (enen though thenumber is high or low in the range), the inertia energy of the engine 2is cancelled with each other by operating the compression reaction forceand the reaction force occurring by the negative pressure with eachother. Therefore, the crank angle can be promptly and reliablycontrolled to the optimal crank angle stop position. When the crankangle can be controlled to the optimal crank angle stop position, themotor generator 3 can execute the automatic restart of the engine 2 bythe minimum outputting torque (starting load). Thereby, the startingperformance of the engine 2 can be improved.

Next, a flow of the engine stop control according to this embodimentwill be explained with reference to FIG. 7. FIG. 7 is a flow chart ofthe engine stop control according to the first embodiment. It is notedthat the engine stop control described hereafter is executed by the ECU70 which detects the output signals of various sensors shown in FIG. 2.

First, the ECU 70 determines whether or not the accelerator is OFF,based on a detection signal of an accelerator opening sensor 76 (stepS1). When the accelerator is OFF, the number of engine revolutionbecomes the number of idling revolution, as shown by time t0 to t1 inFIG. 5. Next, the ECU 70 determines whether or not the brake is ON,based on the output of the brake switch 78 (step S2). When the brake isON, the ECU 70 executes the fuel cut (step S3), and the number of enginerevolution goes down as shown by time t1 to t2 in FIG. 5.

While the number of engine revolution is going down, the ECU 70 monitorsthe number of engine revolution NE based on the output of the enginerevolution number sensor 80, and determines whether or not the number ofengine revolution NE reaches the predetermined motor setting number ofrevolution NE2 (step S4). When the number of engine revolution NEreaches the motor setting number of revolution NE2, the ECU 70 switchesthe driving force of the engine to the motor generator 3 as shown inFIG. 5, and starts the motoring (step S5). The ECU 70 continues themotoring for a predetermined time (step S6). After continuing themotoring for the predetermined time, which corresponds to time from t2to t3 in FIG. 5, the motoring is stopped (step S7). When the motoring isstopped, the engine rotates by the inertia energy corresponding to thenumber of engine revolution at that time. As explained above, thereversal of the rotation occurs twice by the compression reaction forceand the reaction force of the negative pressure in the cylinder, andfinally the engine stops at the optimal crank angle stop position.

It is preferred that the motoring in step S7 is stopped at the time whenthe predetermined cylinder reaches the top dead center or after thepredetermined cylinder passes the top dead center. This is because, whenthe motoring is stopped before the top dead center, there is aprobability that the rotation of the crankshaft is locked at thatposition.

1st APPLICATION EXAMPLE

Next, the description will be given of an application example of theengine stop control according to this embodiment. In this embodiment,when the number of engine revolution NE reaches the motor setting numberof revolution NE2, the motoring is executed for the predetermined time,so that the number of engine revolution NE becomes the predeterminedmotor setting number of revolution NE2 when the motoring is stopped.However, the output of the motor generator 3 may lower because ofdeterioration of the power supply unit (battery), and the number ofengine revolution at the time of stopping the motoring may be lower thanthe motor setting number of revolution NE2. When the number of enginerevolution is lower than the motor setting number of revolution NE2, theengine cannot be stopped at the optimal crank angle stop positionbecause the scheduled inertia energy cannot be by driving the motorgenerator 3, even after the usual motoring stopping timing. Thereby, itis possible that the inertia energy which is insufficient due to thelowered number of engine revolution is supplemented and the engine isstopped at the optimal crank angle stop position.

Concretely, there are two methods for adding the correction torque. Aflow chart in FIG. 8 shows the first method. In FIG. 8, steps S1 to S6are identical to the engine stop control in FIG. 7. After the motoringis executed for the predetermined time in steps S5 and S6, the ECU 70determines whether or not the number of engine revolution NE is lowerthan the motor setting number of revolution NE2 (step S10). When it islower, the motoring is not stopped at once and the correction torque isadded by the motor generator 3 (step S11). In this case, the motorgenerator 3 is driven at the number of engine revolution at which thenecessary correction torque can be obtained. In a state that the numberof engine revolution NE reaches the motor setting number of revolutionNE2, the motoring is stopped (step S12).

A flow chart in FIG. 9 shows the second method. In FIG. 9, steps S1 toS7 are identical to the engine stop control shown in FIG. 7. Afterstopping the motoring in step S7, the ECU 70 detects the crank angle atthe top dead center at which the motoring is about to be stopped, anddetermines whether or not the crank angle is lower than thepredetermined value (e.g., 140° CA) (step S15). When the crank angle islower than the top dead center at which the motoring is about to bestopped, the crank angle is not within the suitable range shown in FIG.6 at the next top dead center of the cylinder. Therefore, it isdetermined that the engine cannot be stopped at the optimal crank anglestop position, and the correction torque is added by the motor generator3 (step S16).

As explained above, according to the first application example, if thenumber of engine revolution is lower than the motor setting number ofrevolution after stopping motoring, the correction torque by the motorgenerator 3 is added to reliably execute the stop control.

2nd APPLICATION EXAMPLE

The second application example relates to a processing when engine startis requested during the engine stop control according to theabove-described first embodiment. It is noted that the engine restart isrequested during the idling stop, for example, when the driver releasesthe brake, or when the predetermined time elapses from the brake offoperation, or when the accelerator is ON, or the like.

First, with reference to a flow chart in FIG. 7, when the engine startis requested during the fuel cut (step S3) in the engine stop control,the ECU 70 may cancel the fuel cut and restart the fuel injection. Inthis case, if the number of engine revolution is lower than thepredetermined number of engine revolution, it is preferred that theassist of the driving force is executed by the motor generator 3 toimprove the starting performance.

Next, when the engine start is requested during the motoring (step S5)in the engine stop control, the ECU 70 may restart the fuel injectionwith continuing the motoring to keep the number of engine revolution,and switch the driving source from the motor generator 3 to the engine2.

On the other hand, when the engine start is requested after stopping themotoring, it is preferred that the restart is performed after the engineis once stopped at the optimal crank angle stop position by executingthe stop control as scheduled. This is because uncertain factors maytake place. An example of the uncertain factor is that, if the controlis executed by utilizing the motor generator after the motoring isstopped, the engine stops at the position other than at the optimalcrank angle stop position, and a large torque is needed for the nextrestart.

As described above, in the second application example, when the enginestart is requested during the engine stop control, it is possible topromptly and reliably correspond the engine start request if theappropriate processing is executed corresponding to the stage of theengine stop control.

When the engine start is requested, the fuel injection may be restartedeven during the motoring because the engine stop control is not neededany longer. Conversely, it is preferred that the fuel injection isinhibited during the engines top control, unless the engine start isrequested. The reason is as follows. If the fuel injection is performedeven if the engine stop control is continued, controlling the number ofengine revolution becomes difficult due to the increase of the number ofengine revolution by the explosion energy. Accordingly, it becomesdifficult to keep the number of engine revolution constant, i.e., tokeep the inertia energy of the engine constant, at the time when themotoring is stopped.

3rd APPLICATION EXAMPLE

The third application example relates to a processing in such a casethat, even though the above-described engine stop control is executed,inertia energy of the engine after stopping the motoring becomes largerthan expected, and the position of the engine is expected to get overthe top dead center, which usually cannot be got over by the compressionreaction force. According to the engine stop control of the firstembodiment, by stopping the motoring after the number of motoring engineis kept to the predetermined motor setting number of revolution by themotoring, the engine is always stopped by the identical inertia energy.After stopping the motoring, the crank angle cannot get over the nexttop dead center, as explained with reference to FIG. 6, and the crankangle is finally stopped at the predetermined optimal crank angle stopposition by the reaction force.

However, after stopping the motoring, if the crank angle is expected toget over the next top dead center by the larger inertia energy of theengine than expected, due to a certain cause, a braking operation isperformed by driving the engine in the reverse rotation direction by themotor generator 3. Thereby, the engine can be stopped at the scheduledoptimal crank angle stop position by decreasing the inertia energy. Onthe other hand, if it is still expected that the crank angle gets overthe next top dead center irrespective of performing the above brakeoperation, the rotation of the crankshaft in the normal rotationdirection is assisted by the motor generator 3 to get over the next topdead center. After that, the engine stop control may be retried from thestep of the motoring.

The ECU 70 can determine whether or not the crank angle gets over thenext top dead center, based on values of the number of enginerevolution, the variation of the crank angle, the mission range, the oiland water temperature, the negative pressure in the intake pipe, and thelike. For example, when the number of engine revolution is higher thanscheduled, or when the variation of the crank angle is too large, it canbe determined that the crank angle may get over the next top dead centerwith high probability.

FIG. 10 shows a flow chart of the engine stop control according to thisapplication example. In FIG. 10, steps S1 to S7 until the motoring stopare identical to the processing of the first embodiment shown in FIG. 7.After the motoring is stopped, the ECU 70 determines whether or not thecrank angle gets over the next top dead center, based on the detectedresult, such as the above-described the number of engine revolution(step S20). If it is determined that the crank angle gets over the nexttop dead center, the ECU 70 performs the brake operation by the motorgenerator 3, and determines again whether the crank angle still getsover the next top dead center (step S22). If it is determined that thecrank angle still gets over the next top dead center even after thebrake operation operation, the ECU 70 execute the assist in the normaldirection by the motor generator 3, and returns to step S5 to try theprocessing again from the motoring.

As described above, in this example, when the engine stop control isexecuted as scheduled, if it is determined that the crank angle getsover the next top dead center by a certain cause, the reliability of thestop position control can be improved by performing the brake operationand the assist operation and the like by the motor generator 3.

4th APPLICATION EXAMPLE

The forth application example is a processing by taking account of thenumber of idling revolution in the above-described engine stop control.In the above-described engine stop control, when the accelerator is madeOFF, the number of engine revolution becomes the number of idlingrevolution NE1, as shown in FIG. 5. Here, the ECU 70 checks the numberof idling revolution NE1, and does not execute the engine stop controlwhen the number of idling revolution NE1 is larger than thepredetermined number of revolution (e.g., it is prescribed as NE3).Concretely, when the number of idling revolution NE1 is larger than thepredetermined number of engine revolution NE3, the ECU 70 does not setthe fuel cut signal (engine stop permission signal) to H level, and doesnot execute the fuel cut. The reason is as follows. When the number ofidling revolution NE1 is too high, since the time period from the fuelcut until the engine stop becomes longer, the negative pressure in theintake pipe is almost equivalent to the atmospheric pressure, and thenegative pressure is insufficient. As a result, the load of the motoringby the motor generator 3 increases, the control of the number of enginerevolution becomes unstable, and finally it is possible that the engineis not stopped at the optimal position. Therefore, the ECU 70 checks thenumber of idling revolution NE1, and does not output the fuel cut signalwhen the number of idling revolution is larger than the predeterminednumber of engine revolution NE3, so as to avoid the failure of theabove-described stop control.

On the other hand, when the detected number of idling revolution issmaller than the predetermined value (e.g., it is prescribed as NE4),the ECU 70 increases the fuel for injection without performing the fuelcut at once, thereby to increase the number of engine revolution, eventhough the brake is ON. Then, the ECU 70 outputs the fuel cut signalwhen the number of engine revolution becomes larger than thepredetermined value NE4, and executes the fuel cut, and executes theengine stop control thereafter. If the number of idling revolution istoo low when the accelerator is OFF, the negative pressure in the intakepipe is still large near the time of stopping the engine. As a result,the compression reaction force becomes small, and it is presumed thatstopping the engine at the optimal position with the inertia energybecomes difficult. Therefore, when the number of idling revolution issmaller than the predetermined value NE4, first, the number of enginerevolution is increased to the predetermined value NE4 by increasing thefuel injection amount, and then the motoring is stopped to execute theengine stop control.

The above-described processing is explained with reference to a flowchart in FIG. 11. In FIG. 11, steps S1 to S7 are basically identical tothe processing of the basic engine stop control of the first embodimentshown in FIG. 7. In FIG. 11, after the brake is made ON in step S2, theECU 70 detects the number of engine revolution (the number of idlingrevolution) (step S2-1), and determines whether the detected number isproper, or larger than the predetermined value NE3 or smaller than thepredetermined value NE4 (step S2-2). When the detected number is proper,the processing moves to step S3, and performs the fuel cut to continuethe engine stop control. On the other hand, when the number of idlingrevolution is too high, i.e., higher than the predetermined value NE3,the processing returns to step S2-1 to wait for the number of idlingrevolution to lower, or cancels the engine stop control itself (stepS2-4). Even if the engine stop control is canceled, it only means thatthe idling stop of the vehicle is not executed, and there is noparticular problem. When the number of idling revolution is lower thanthe predetermined value NE4, the ECU 70 increases the fuel injectionamount (step S2-3), and increases the number of engine revolution to theproper value. After that, the fuel cut is performed (step S3).

As explained above, in the fourth application example, a probability ofthe successful engine stop control can be increased, when the number ofidling revolution after the accelerator off is too high and too low.

5th APPLICATION EXAMPLE

The fifth application example is based on the engine stop controlaccording to the first embodiment and is to shorten the energizing timeto the motor generator during the motoring by unifying the cylinderssubjected to the fuel cut. Concretely, in executing the engine stopcontrol of the first predetermined number, the cylinder subjected to thefuel cut is randomly determined, and the engine stop control accordingto the first embodiment is executed by performing the fuel cut for thedetermined cylinder. At this time, an actual energizing time to themotor generator is recorded for each cylinder. After the predeterminednumber of engine stop control is executed, the fuel cut is performed forthe cylinder having the shortest energizing time to the motor, accordingto the record until then.

Thereby, if the fuel cut is performed by the specific cylinder among theplurality of cylinders in the engine 2, the energizing time to the motorgenerator can be the shortest.

It is noted that the cylinder subjected to the fuel cut can bedetermined not only by the above-described motor energizing time, butalso by taking account of the number of idling revolution, the missionrange, the past stop situation, a cylinder pressure estimated result byair pressure, the oil and water temperature, and the like.

2nd Embodiment

Next, the second embodiment of the present invention will be explained.In the above-described first embodiment, at the time of the idling stop,the number of engine revolution is kept within the predetermined rangeby motoring after performing the fuel cut of the engine. Then, themotoring is stopped, and the engine is controlled at the optimal stopposition by the inertia energy.

To the contrary, in the second embodiment, a transition of the idealnumber of engine revolution for stopping the engine at the optimal stopposition is preset. After the fuel cut, while monitoring the number ofengine revolution, the brake and the assist operation are performed bythe motor generator as the need arises to control the actual number ofengine revolution to follow the ideal number of engine revolution.

FIG. 12 shows a variation example of the number of engine revolutionduring the engine stop control according to the second embodiment. In agraph of the number of engine revolution in FIG. 12, the solid line 120indicates an ideal transition of the number of engine revolution in theembodiment, and the broken line 130 indicates an actual transition ofthe number of engine revolution. In the embodiment, an assist/brakeoperation by the motor generator is performed so that the actual numberof engine revolution follows the ideal transition line 120 of the numberof engine revolution. It is noted that “assist” is to give the drivingforce in the normal rotation direction of the engine by the motorgenerator, and “brake” is to give the driving force in the reverserotation direction of the engine by the motor generator.

In FIG. 12, the accelerator of the vehicle is made OFF at time t0, thebrake is set ON at time t1, and the ECU 70 performs the fuel cut. Thoughthe number of engine revolution is automatically decreased after thefuel cut, the ECU 70 determines whether or not the number of enginerevolution is on the ideal transition line 120 of the number of enginerevolution by continuously monitoring the number of engine revolution.When the actual number of engine revolution deviates from the idealtransition line 120 of the number of engine revolution, the ECU 70performs the assist or brake operation by driving the motor generator 3to follow the ideal transition line 120 of the number of enginerevolution by increasing or decreasing the actual number of enginerevolution. Finally, by removing the driving force by the motorgenerator 3 at the predetermined number of engine revolution, the engineis stopped at the optimal crank angle stop position by utilizing theinertia energy.

According to the method, if the ideal transition line of the number ofengine revolution is preset so that the engine can be stopped at theoptimal crank angle stop position with high probability, and the actualnumber of engine revolution is controlled to follow the line by theassist/brake operation by the motor generator, the engine stop controlcan be stably executed. Since the number of engine revolution iscontrolled on real-time basis by the motor generator, stable engine stopcontrol can be realized, even when the number of engine revolution isunstable by a certain temporary cause.

FIG. 13 shows an example a flow chart of the engine stop controlaccording to the second embodiment. In FIG. 13, steps S51 to S53 areidentical to steps S1 to S3 of the engine stop control of the firstembodiment shown in FIG. 7. When the fuel cut is performed, the ECU 70detects the number of engine revolution, and compares the number ofengine revolution with the ideal number of engine revolution which isprescribed by the ideal transition line 120 of the number of enginerevolution (step S54). When the actual number of engine revolution islower than the ideal number of engine revolution, the assist operationis performed by the motor generator 3 (step S55). When the actual numberof engine revolution is higher than the ideal number of enginerevolution, the brake operation is performed by the motor generator 3(step S56). When the actual number of engine revolution is proper, thedriving by the motor generator 3 is not executed. In that way, theactual number of engine revolution is controlled to follow the idealline 120 of the number of engine revolution, and when the number ofengine revolution reaches the predetermined number of engine revolution(step S57; Yes), the motoring is stopped (step S58). Afterward, theengine stops at the optimal crank angle stop position by the inertiaenergy of the engine.

3rd Embodiment

The third embodiment is based on the engine stop control and is toimprove control accuracy by removing as many energy loads as possible.This embodiment can be applied to both the first and second embodiments.

If the engine load, such as auxiliary machines and the like, is largewhen executing the engine stop control according to the presentinvention, the fuel consumption improving effect by the idling stopbecomes low because the energy for controlling the number of enginerevolution is large. Also, if there is any engine load, the number ofengine revolution can vary dependently upon the variation of the load.As a result, controlling the number of engine revolution is unstable,and finally the probability that the engine stop control fails becomeshigher. Therefore, in this embodiment, when starting the engine stopcontrol, the engine load is made as small as possible.

“Engine load” includes various kinds of loads, for example, an airconditioner, an electric power steering, front lights and so on. Namely,as the processing for reducing the engine load, inhibiting the powergeneration by a generator, switching off the front lights, andinhibiting the air conditioner operation are included, for example. Asthings affecting the number of engine revolution, the ON/OFF control ofa control valve (it is called “ISC”) which is provided in the engine foradjusting the number of idling revolution, and electron throttle controlare also included in the engine load.

As described above, by making the engine load as small as possible whenexecuting the engine stop control, the number of engine revolution canbe controlled with high accuracy, and the engine stop control can bemore reliably executed. Also, the energy needed for controlling thenumber of engine revolution can be reduced. Concretely, in the firstembodiment, by making the engine load small, the accuracy of controllingthe number of engine revolution by the motoring can be improved. In thesecond embodiment, the accuracy for making the actual number of enginerevolution follow the ideal transition line of the number of enginerevolution can be improved by driving the motor generator.

FIG. 14 shows an example of a processing flow chart of a case that theembodiment is applied to the first embodiment. Steps S1 to S7 in FIG. 14are identical to the engine stop control of the first embodiment shownin FIG. 7, and the embodiment is different from the first embodimentonly in that steps S2-6 is inserted. Namely, when the brake operation isdetected in step S2, the ECU 70 executes the above-described processingfor reducing the engine load (step S2-6), and the number of enginerevolution is controlled by performing the fuel cut. Thereby, thecontrol of the number of engine revolution can be executed with highaccuracy.

It is noted that the processing in step S2-6 shown in FIG. 14 may alsobe added after step S52 in FIG. 13 when this embodiment is applied tothe second embodiment.

Though the fuel cut is performed at the time of brake operation in theabove-described examples, it is also possible that the fuel cut in theengine stop control is performed at other timing.

As explained above, according to the engine stop control of the presentinvention, by controlling the number of engine revolution with the motorgenerator at the idling stop time, the engine is stopped at the optimalcrank angle stop position by utilizing the inertia energy of the engine.Therefore, the accuracy of the engine stop control can be improved, andthe energy needed for the stop control can also be reduced.

[Engine Stop and Start Control]

Next, an engine stop and start control according to the presentinvention will be described. The engine stop and start control of theinvention enables early ignition start of the engine.

According to the aforementioned engine stop control, it is possible toestimate, before the engine actually stops, at which stroke eachcylinder stops at the time of engine stop. As shown in FIG. 5, in theabove-described engine stop control, a predetermined motoring period isprovided after the fuel cut to keep the number of revolution of theengine 2 at a predetermined number of revolution, whereby the inertiaenergy which the engine 2 has is made constant at that point of time,and thereafter the motoring is finished to remove the driving force ofthe engine 2 to stop the engine 2. Consequently, how many times theengine 2 rotates until it stops after the motoring is finished dependson the inertia energy which the engine 2 has when the motoring isfinished, i.e., the number of engine revolution kept by the motoring,the motoring period and the like. Conversely, since the number ofrevolution during the motoring is kept constant, how many times theengine rotates before the engine (i.e., crankshaft) stops after themotoring is finished always becomes constant.

Consequently, if it is detected to which stroke each of the cylindersbelongs at the time of starting the motoring by the cylinderdiscrimination utilizing the aforementioned cam angle sensor 92 and thelike, it can be estimated in which stroke each of the cylinder is whenthe engine finally stops after the motoring is carried out for apredetermined motoring period. For example, if the inertia energy at thetime of finishing the motoring, i.e., the number of engine revolution atthe time of finishing the motoring is determined so that, for example, acertain cylinder at a specific stroke at the time of finishing themotoring can get over the next compression top dead center, but cannotget over the second compression top dead center, the cylinder is in thecompression stroke when the engine 2 stops. It is known, from themotoring period, how many times the engine 2 rotates during the motoringperiod. Consequently, the ECU 70 can estimate, during execution of theengine stop control, which stroke each of the cylinders are in, at thetime of engine stop, based on the information of the stroke of each ofthe cylinders at the time of the motoring stop or at the time of themotoring start, and the information indicating how many times the engine2 rotates by the inertia energy after the motoring is finished. In thestop and start control of the engine 2 of the present invention whichwill be described hereinafter, an air-fuel mixture is introduced andsealed in the cylinder, which is estimated to be in a specific strokeafter the engine stop, before the engine stop by utilizing theestimation result.

Next, the stop and start control of the engine for early ignition startaccording to the present invention will be described.

4th Embodiment

A fourth embodiment is to perform early start of the engine 2 bypreviously performing fuel injection to a cylinder which is estimated tostop in the compression stroke at the time of engine stop to seal themixture in the combustion chamber, when carrying out the engine stopcontrol at the aforementioned optimal crank angle stop position, and byigniting the mixture in addition to the cranking by the motor generator,at the time of engine start.

First, a basic principal of the embodiment will be explained. In thefirst method, for example, at the time of engine stop such as the idlingstop, the aforementioned engine stop control is performed and it isestimated which stroke each of the cylinder is in at the time of enginestop. Thus, the cylinder that is estimated to be in the compressionstroke when the engine stops is specified. It can be estimated, by theaforementioned method, which stroke each of the cylinders are in at thetime of engine stop.

In a port injection type engine as in the first method, since both theintake and the exhaust valves are normally in the closed state in thecylinder in the compression stroke during engine stop, the mixturecannot be introduced to the combustion chamber of the cylinder after theengine stops, unlike a so-called direct injection type engine. For thisreason, in order to introduce and seal the mixture in the combustionchamber of the cylinder estimated to be in the compression stroke at thetime of engine stop (hereinafter, also called “stop time compressionstroke cylinder”), it is necessary to perform fuel injection in advanceat the intake stroke of the cylinder. Consequently, when, for example,#3 cylinder is estimated to be in the compression stroke at the time ofengine stop, the ECU 70 performs the fuel injection for the cylinder inthe intake stroke preceding the compression stroke, and seals themixture in the combustion chamber in advance. At the point of time whenthis fuel injection is performed, the engine is not stopped yet, and theinside of the combustion chamber of the cylinder in the intake stroke isunder negative pressure. Therefore, the mixture containing fuel injectedin the intake port can be reliably introduced into the combustionchamber. As a result, the engine stop control is completed, and when theengine stops, the mixture is sealed inside of the combustion chamber ofthe stop time compression stroke cylinder (#3 cylinder in this example).

At the time of engine start, the ECU 70 performs cranking by the motorgenerator 3, and ignites the stop time compression stroke cylinder (#3cylinder) to generate explosion energy to rotate the crankshaft, wherebythe early start of the engine 2 can be performed.

The mixture which is thus sealed in the stop time compression strokecylinder at the time of engine stop has a favorable air-fuel ratio basedon the A/F sensor output during engine stop control, i.e., before theengine stop. Also, as described in the explanation of the aforementionedengine stop control, since the rotation of the engine is reversedimmediately before the engine is stopped by utilizing the inertiaenergy, the sealed mixture is subjected to the repeated compression andexpansion by the piston in the combustion chamber, and is in a state inwhich air and fuel are mixed well. Further, the engine is still in awarmed-up state after the engine stops, and therefore the mixturegenerates convection inside the combustion chamber by receiving heatfrom the cylinder, which promotes mixing of the air and the fuel. Forthese reasons, the atomized homogenous mixture is kept in the combustionchamber, and the mixture is in an easily ignitable state. Consequently,the mixture is combusted smoothly by the ignition at the time of theengine start, and the early start of the engine can be achieved.

Next, the fourth embodiment will be explained in detail with referenceto FIGS. 15 to 18. First, the description will be given of a method ofthe stop control for the early ignition start according to the fourthembodiment of the engine start and stop control according to theinvention. FIG. 15 shows an example of the stop control according to theembodiment, and FIG. 16 is a flow chart thereof.

FIG. 15 is a stroke chart showing a state of each of the cylinders justbefore the engine stops, and a time chart corresponding to the strokechart. In FIG. 15, the stop time compression stroke cylinder is assumedto be the #3 cylinder. In the first method, an example of afour-cylinder engine is described, but the application of the presentinvention is not limited to this. The firing order of the engine 2 is,for example, #1 cylinder-#3 cylinder-#4 cylinder-#2 cylinder, but theapplication of the present invention is not limited to this.

The engine stop control here is basically the same as what is explainedabove with reference to FIG. 5 and FIG. 6. Namely, after the driverreleases the accelerator, the fuel cut signal is turned on at the timeof braking (time t1), and the fuel cut is performed. As a result, thefuel injection is not performed after the time t1 as a rule. Thereafter,when the number of engine revolution goes down to a predeterminednumber, the MG drive signal is turned on at time t2, and the motoring isstarted. After a predetermined time elapses, the motoring finishes attime t3, and thereafter the engine shows the behavior shown in FIG. 6and stops at time t4. The position at which the engine stops is shown bythe broken line as an actual stop position in FIG. 15.

In the engine stop state, the #3 cylinder which is the stop timecompression stroke cylinder is in the compression stroke. The ECU 70already estimates this during engine stop control, for example, at thetime of starting the motoring. The ECU 70 performs fuel injection to the#3 cylinder, which is the stop time compression stroke cylinder, in theintake stroke just before the engine stop (see the arrow 210). Namely,as known with reference to the fuel cut signal, though the fuelinjection is not performed after the level change of the fuel cut signalas a rule, the fuel cut is temporarily intermitted and the fuel isexceptionally injected (time t5 to t6) only while the stop timecompression stroke cylinder belongs to the intake stroke just before theengine stop, in order to introduce and seal the mixture in the stop timecompression stroke cylinder. As a result, the mixture is sealed in the#3 cylinder which is in the compression stroke at the time of enginestop. In the vicinity of the engine stop at the time t4, the ECU 70turns on the ignition cut signal, and stops the ignition in all thecylinders.

Next, the start control performed after the engine stops in that waywill be explained with reference to FIG. 16. FIG. 16 is a stroke chartshowing an example of the start control of the engine 2 after the enginestop control. The actual stop position shown in FIG. 16 is the same asthe actual stop position shown in FIG. 15.

As shown in FIG. 8, the #4 cylinder is in the intake stroke at theactual stop position. Consequently, in order to carry out early start ofthe engine 2, the ECU 70 turns off the fuel cut signal when the enginestart condition is established, and executes fuel injection through theEFI into the combustion chamber of the #4 cylinder in the intake stroke(see the arrow 220).

In the actual stop position, the #3 cylinder is in the compressionstroke as mentioned above, and the mixture is sealed in the combustionchamber of the #3 cylinder. Consequently, the ECU 70 ignites the mixturesealed in the combustion chamber of the #3 cylinder to rotate thecrankshaft (see the arrow 221). Specifically, the ECU 70 shifts theignition cut signal from ON to OFF when the engine starting condition isestablished, and transmits the ignition command signal to the igniterwhen the #3 cylinder reaches the compression top dead center. By this,the ECU 70 rotates the crankshaft by the combustion pressure generatedat that time. Thereafter, the fuel injection and ignition are executedas usual.

As described above, according to the fourth embodiment, at the time ofthe engine start, the mixture sealed in the stop time compression strokecylinder at the time of engine stop is combusted to generate explosionenergy to drive the crankshaft, in addition to the cranking by the motorgenerator. Thus, early initial explosion of the engine 2 is realized,and the engine can be started quickly.

Next, a flow chart of the stop control according to the fourthembodiment will be explained with reference to FIG. 17. The ECU 70basically executes the control, based on the output signal from varioussensors.

In sequence, in step S71, the ECU 70 determines whether or not theengine stop condition is satisfied, by monitoring the output signalstate of the brake pedal switch and whether or not the number of enginerevolution is equivalent to the predetermined number of enginerevolution as a determination standard. Concretely, when the brakeswitch interlocking the brake pedal is ON and the number of enginerevolution is in the predetermined range of number of engine revolution(e.g., around 0(rpm)), the ECU 70 determines that the engine stopcondition is satisfied based on the output signal from the sensorsdetecting those states (step S71; Yes). Thereby, the processing moves tostep S72. On the other hand, when the brake switch is OFF or the numberof engine revolution is not in the predetermined range of number ofengine revolution (e.g., about 0(rpm)), the ECU 70 determines that theengine stop condition is not satisfied, based on the output signals fromthe sensors detecting those state (step S71; No). Therefore, until theengine stop condition is satisfied, the processing does not move to stepS72.

Next, in step S72, the ECU 70 performs the fuel cut to each cylinder. Instep S73, the ECU 70 determines whether or not starting the motoring ispossible, by comparing the number of engine revolution with thepredetermined number of engine revolution. When the number of enginerevolution becomes smaller than the predetermined number of enginerevolution, the processing moves to step S74, the ECU 70 drives themotor generator 3 via the motor control unit 4 to stat the motoring(step S73; Yes). Concretely, the ECU 70 sends a command signalcorresponding to a predetermined motoring execution period to the motorcontrol unit 4, and the motor control unit 4 controls the motorgenerator 3 based on the command signal. Thereby, the motoring isexecuted for the predetermined time period. On the other hand, when thenumber of engine revolution is larger than the predetermined number ofengine revolution, the processing does not move to step S74 until thenumber of engine revolution becomes smaller than the predeterminednumber of engine revolution (step S73; No).

Next, in step S75, as described above, the ECU 70 estimates the stoptime compression stroke cylinder, based on the cylinder determinationsignal at the time of starting the motoring and the above-mentionedpredetermined motoring execution period. It is noted that the ECU 70estimates #3 cylinder to be the stop time compression stroke cylinder inthe embodiment. Afterward, in order to perform the fuel injection in theintake stroke of the cylinder immediately before the engine stop, theECU 70 continuously detects in which stroke #3 cylinder is, based on theoutput signal from the cam angle sensor 92. In step S76, the ECU 70determines whether or not the stop time compression stroke cylinder,i.e., #3 cylinder, is in the intake stroke. When #3 cylinder is in theintake stroke, the processing moves to step S77 (step S76; Yes). On theother hand, while #3 cylinder is not in the intake stroke, theprocessing does not move to step S77 until #3 cylinder comes to theintake stroke (step S6; No).

Next, in step S77, the ECU 70 executes the fuel injection of thepredetermined amount, via the EFI, to the combustion chamber of the stoptime compression stroke cylinder, i.e., the combustion chamber of #3cylinder in the intake stroke. When the fuel injection is completed(step S78; Yes), the processing moves to step S79.

Next, in step S79, when the ECU 70 detects a motoring stop commandsignal from the motor control unit 4, the processing moves to step S80to stop the motoring. The motoring stop command signal is transmittedfrom the motor control unit 4 to the ECU 70, when the predeterminedmotoring execution period set in step S74 has elapsed. On the otherhand, the processing does not move to step S80 until the motoring stopcommand signal is detected (step S79; No). Next, in step S81, the ECU 70executes the ignition cut to each cylinder, via the EFI. Afterward, theengine 2 shows the behavior as shown in FIG. 6 and stops (step S82).

In that way, by the stop control of this invention, the crank anglebecomes the optimal crank angle position, and the engine stops with themixture being introduced and sealed in the combustion chamber of thestop time compression stroke cylinder.

Next, the description will be given of a flow chart of the engine startcontrol according to the fourth embodiment, with reference to FIG. 18.First, in step S101, the ECU 70 determines whether or not thepredetermined engine start condition is satisfied, e.g., the ignitionswitch is ON and the brake pedal switch is ON (step S101). When theengine start condition is satisfied, the ECU 70 executes the motoring(cranking) by the motor generator 3 (step S102). Also, the ECU 70detects a cylinder in the intake stroke at the time of the engine stop(hereafter, it is also called “stop time intake stroke cylinder”), basedon the output signal from the cam crank sensor 92 and the like, andexecutes the fuel injection (step S103). Further, the ECU 70 executesthe ignition to the stop time compression stroke cylinder (step S104).Since the mixture is introduced and sealed in the stop time compressionstroke cylinder as described above, the combustion starts at once, andthe revolution of the crankshaft can be obtained by the explosionenergy. Thereby, it becomes possible that the time until the firstexplosion is quite shortened to realize the early ignition start of theengine 2. In that way, the engine 2 starts.

As explained above, according the fourth embodiment of the engine stopand start control of the present invention, by estimating, during theengine stop control, the cylinder in the compression stroke at the timeof the engine stop, the mixture is introduced into the combustionchamber by injecting the fuel into the cylinder. Therefore, at the timeof the engine start, the combustion can be started at once in thatcylinder to early start the engine.

5th Embodiment

The fifth embodiment is intended to realize early ignition start of theengine 2 more quickly, by utilizing the engine stop and start controlaccording to the aforementioned fourth embodiment as a base.Specifically, in the fifth embodiment, the fuel injection is performed,in advance, for the cylinder estimated to stop in the expansion strokeat the time of engine stop (hereinafter, also called “stop timeexpansion stroke cylinder”) thereby to seal the mixture at the time ofengine stop. At the time of the engine start, normal pressure ignitionis performed for the mixture, thereby earlier start of the engine isperformed. Here, the normal pressure ignition means that the ECU 70ignites not the mixture in the compressed state by the normalcompression stroke, but to the mixture in the combustion chamber in theexpansion stroke near the atmospheric state through the EFI.

Explaining the outline of the fifth embodiment, first, during the enginestop control, the stop time compression stroke cylinder and the stoptime expansion stroke cylinder are estimated. When it is estimated thatthe #1 cylinder is in the expansion stroke and the #3 cylinder is in thecompression stroke during the engine stop, for example, the ECU 70performs the fuel injection to these cylinders, respectively, in theintake stroke just before the engine stop, and the mixture is sealed ineach of the combustion chamber. Consequently, when the engine stopsafter the engine stop control is completed, the mixture is sealed andretained in the combustion chamber of each of the cylinder. In addition,the mixture becomes favorably atomized mixture by the reverse movementof the engine at the time of the engine stop, the convention effect byheat received from the cylinder and the like, and is in an easilyignitable state.

Consequently, when the engine start condition is established thereafter,the ECU 70 first drives the motor generator 3 to perform cranking, andstarts to ignite the stop time compression stroke cylinder and the stoptime expansion stroke cylinder. This enables to start the engine 2 byutilizing the explosion energy of the stop time expansion strokecylinder in addition to the driving energy of the motor generator andthe explosion energy of the stop time compression stroke cylinder, andhence the start of the engine 2 can be more quick and reliable.

Next, an example of the engine stop control according to the fifthembodiment will be explained with reference to FIG. 19. As shown in FIG.19, the engine stop control of the fifth embodiment is different fromthe engine stop control (see FIG. 15) according to the fourth embodimentin that the fuel injection is also performed for the #1 cylinder, whichis the stop time expansion stroke cylinder, after the fuel cut isexecuted at the time t1. Namely, in the engine stop control, the fuelcut is executed at the time t1, and the motoring by the motor generatoris started when the number of engine revolution goes down to apredetermined number at the time t2. Thereafter, the fuel cut istemporarily intermitted at the time t5 when the #1 cylinder which is thestop time expansion stroke cylinder is in the intake stroke just beforethe engine stop, and the fuel injection is performed for the #1 cylinder(arrow 211). Subsequently, the fuel injection is also performed for the#3 cylinder which is the stop time compression stroke cylinder (arrow210), in the similar manner. When the fuel injection to these twocylinders is completed, the fuel cut is carried out again at the timet6. The motoring is finished at the time t3, and the engine stops at thetime t4.

Next, an example of the engine start control according to the fifthembodiment will be explained with reference to FIG. 20. In FIG. 20, whenthe engine start condition is established, the fuel cut signal is turnedoff to start the fuel injection, and the ignition cut signal is turnedoff to carry out the ignition. Since the mixture is sealed in the #3cylinder which is the stop time compression stroke cylinder and the #1cylinder which is the stop time expansion stroke cylinder during enginestop shown at the actual stop position in FIG. 20, the #1 cylinder isignited (arrow 221) and the #3 cylinder is ignited (arrow 220) at thetime of engine start, and the driving force by the explosion energy isgenerated. The explosion energy is added to the cranking by the motorgenerator, and therefore early start of the engine can be achieved.

Next, the description will be given of a flow chart of the engine stopcontrol according to the fifth embodiment, with reference to FIG. 21.FIG. 21 is the flow chart of the stop control according to theembodiment. It is noted that the ECU 70 basically executes the control,based on the output signal from various sensors. In the embodiment, theexplanation will be given by simplifying the identical portions to thefourth embodiment.

Since steps S201 to S204 are identical to steps S71 to S74 in the flowchart of the stop control method according to the forth embodiment (seeFIG. 17), the explanation is omitted.

Next, in step S205, the ECU 70 estimates the stop time compressionstroke cylinder and the stop time expansion stroke cylinder, based onthe cylinder determination signal at the time of the motoring start andthe predetermined motoring execution time. In the embodiment, asexplained with reference to FIG. 19, the ECU 70 estimates that #1cylinder stops in the expansion stroke and #3 cylinder stops in thecompression stroke at the time of the engine stop. Next, the ECU 70constantly detects in which strokes #1 and #3 cylinders are at thistime, based on the output signal from the cam angle sensor 92 and thelike.

In step S206, the ECU 70 determines whether or not the stop timeexpansion stroke cylinder, i.e., the detected #1 cylinder, is in theintake stroke. When #1 cylinder is in the intake stroke, the processingmoves to step S207, and the ECU 70 executes the fuel injection of thepredetermined amount, to the stop time expansion stroke cylinder, i.e.,#1 cylinder. When the fuel injection is completed, the processing movesto step S209 (step S208; Yes). Thereby, at the time of the engine stop,#1 cylinder stops with the mixture being introduced and sealed in thecombustion chamber.

Steps S209 to S211 are identical to steps S76 to S78 of the flow chartof the stop control method according to the fourth embodiment (see FIG.17). Namely, the ECU 70 executes the fuel infection of the predeterminedamount in the intake stroke, to the stop time compression strokecylinder, i.e., #3 cylinder. Thereby, at the time of the engine stop, #3cylinder stops with the mixture being introduced and sealed in thecombustion chamber.

Next, in step S212, the ECU 70 executes the ignition cut to eachcylinder. In step S213, when the ECU 70 detects the motoring stopcommand signal from the motoring control unit 4, the ECU 70 stops themotoring (step S214). It is noted that the motoring stop command signalis transmitted from the motor control unit 4 to the ECU 70, when thepredetermined motoring execution period lapses. Then, the engine 2 stops(step S215). In that way, when the engine stops, #1 cylinder is in theexpansion stroke, and #3 cylinder is in the compression stroke. In thiscase, the mixture is introduced and sealed in both cylinders.

Next, the description will be given of the engine start method accordingto the fifth embodiment. FIG. 22 is a flow chart of the engine startcontrol according to the embodiment. It is noted that the ECU 70basically executes the control, based on the output signal from varioussensors. In the embodiment, the explanation will be given by simplifyingthe identical portions to the fourth embodiment.

In step S301, the ECU 70 determines whether or not the engine startcondition is satisfied. When the engine start condition is satisfied,the ECU 70 starts the motoring by the motor generator 3 (step S302).

In step S303, the ECU 70 detects the stop time expansion stroke cylinder(#1 cylinder) based on the output signal from the cam angle sensor 92and the like, and transmits the ignition command signal to the igniterto perform the ignition (normal pressure ignition) to the mixture in thecombustion chamber of the stop time expansion stroke cylinder (#1cylinder). Thereby, the driving force of the crankshaft is generated.

Based on the output signal from the cam angle sensor 92, the ECU 70executes the fuel injection to the stop time intake stroke cylinder(step S304). Further, the ECU 70 performs the ignition to the stop timecompression stroke cylinder (step S305). Since the mixture is introducedand sealed in the stop time compression stroke cylinder as mentionedabove, the combustion starts at once, and the revolution of thecrankshaft can be obtained by the explosion energy. In that way, theengine 2 starts.

As explained above, in the second embodiment, by estimating, during theengine stop control, the cylinders in the compression stroke and theexpansion stroke at the time of the engine stop, the fuel is injected tothose cylinders and the mixture is introduced and sealed in theircombustion chambers. Thus, at the time of the engine start, it ispossible that the combustion starts at once in the cylinders to enablethe early start of the engine.

In the embodiment, the early engine start is realized by utilizing theexplosion energy of the stop time expansion stroke cylinder, in additionto the cranking by the motor generator and the explosion energy of thestop time compression stroke cylinder. As explained above, at the timeof the engine start, first, the cranking is executed by the motorgenerator. However, in a case of the drive by the motor generator,rise-up of exciting current becomes slow when the charged voltage of thebattery driving the motor generator is low. At this time, it may take arelatively long time until the maximum torque of the motor generator canbe outputted. At this point, like the embodiment, if the engine isstarted by utilizing the explosion energy of the stop time expansionstroke cylinder in addition to the energy of the motor generator, theexplosion energy can be obtained at once at the time of the enginestart. As understood from FIG. 20, this is because the combustion of thestop time expansion stroke cylinder is executed at once (arrow 221),though the combustion of the stop time compression stroke cylinder(expansion stroke) is executed later in time (arrow 220). Therefore,when the torque output by the motor generator is late reason, thisembodiment is particularly advantageous in that the time until theengine start can be shortened by the explosion energy of the stop timeexpansion stroke cylinder.

While the above-described fifth embodiment is to generate the explosionenergy at the time of the engine start by introducing the mixture in thestop time compression stroke cylinder and the stop time expansion strokecylinder, it is also possible to utilize the explosion energy byintroducing the mixture only in the stop time expansion stroke cylinder.The explosion energy of the stop time compression stroke cylinder islarge because it utilizes the mixture in the compressed state, like theusual combustion. In contrast, in terms of the energy, the explosionenergy of the stop time expansion stroke cylinder is small because it isthe normal pressure ignition and the uncompressed mixture (likeatmospheric pressure) is used. Therefore, it is preferred that theengine start is accelerated by adding the explosion energy of the stoptime expansion stroke cylinder, in addition to utilizing the explosionof the stop time compression stroke cylinder according to the fourthembodiment.

3rd Embodiment

In the engine start control of the above-described fifth embodiment,first, the cranking by the motor generator is executed, and the enginestart is accelerated by the explosion energy by igniting the stop timecompression stroke cylinder and the stop time expansion stroke cylinder.Therefore, the cranking is executed by adding the explosion energy ofthe stop time expansion stroke cylinder to the driving force of themotor generator. However, when the first ignition (see the arrow 221 inFIG. 20) in the stop time expansion stroke cylinder is failed by acertain cause and ignition failure occurs, the cranking is executed onlyby the motor generator, without obtaining the explosion energy. In thiscase, if the motor generator is driven while the exciting current of themotor generator is not larger than a certain value, the torque neededfor the cranking cannot be obtained, and the motor generator may belocked.

Therefore, in the third embodiment, the rotation start of the crankshaftby the explosion energy of the stop time expansion stroke cylinder,i.e., the variation of the crankshaft is detected, and if the crankangle is not varied during a certain time, the cranking is executed bythe motor generator after the exciting current becomes larger than thepredetermined value. When the crankshaft starts rotating by theexplosion of the stop time expansion stroke cylinder, the motorgenerator is seldom locked, even though the exciting current of themotor generator is somewhat low and the torque is somewhat small.However, when the first ignition in the stop time expansion strokecylinder is failed, the cranking is to be executed only by the motorgenerator. Therefore, in this case, the cranking by the motor generatoris started in a state that the exciting current of the motor generatoris larger than the predetermined value and the torque is obtained sothat the motor generator is not locked.

If the cranking by the motor generator is started after confirming thatthe crank angle starts varying, there is another advantage as follows.If the cranking by the motor generator 3 is executed first, the volumeof the combustion chamber of the stop time expansion stroke cylinderbecomes larger and compression degree of the mixture sealed thereinbecomes smaller, because the crankshaft rotates in the normal directionand the piston operates. In addition, the exhaust valve gradually startsto open according to the operation of the piston in the stop timeexpansion stroke cylinder. Therefore, since the crankshaft is driven bythe motor generator, the probability of the ignition failure becomeshigh, even though the normal pressure ignition of the stop timeexpansion stroke cylinder is executed. Also, even if the ignitionfailure is prevented, the combustion pressure obtained by executing thenormal pressure ignition to the expansion stroke cylinder becomessmaller because the pressure of the mixture in the combustion chamber ofthe stop time expansion stroke cylinder becomes smaller. Thus, in thiscase, the probability that the engine start is failed becomes high, too.Therefore, in the embodiment, when the first normal pressure ignition ofthe stop time expansion stroke cylinder is failed and the variation ofthe crank angle is not detected, the cranking by the motor generator isnot executed until sufficient torque can be obtained by the motorgenerator.

Next, the description will be given of a flow chart of the engine startcontrol according to the sixth embodiment, with reference to FIG. 23. Itis noted that the identical portions to the engine start controlaccording to the fifth embodiment will be explained by simplifying. TheECU 70 basically executes the engine start control, based on the outputsignal from various sensors.

In step S401, the ECU 70 determines whether or not the engine startcondition is satisfied. When the engine start condition is satisfied,current supply to the motor generator is started in step S402. However,the cranking by the motor generator is not executed yet at this time.

Next, in step S403, the ECU 70 detects the crank angle at the time ofthe engine stop, based on the output signal from the crank angle sensor90 and the like. It is noted that this step can be omitted if the crankangle at the time of engine stop is known during the engine stopcontrol. In step S404, the ECU 70 determines the stop time expansionstroke cylinder (#1 cylinder) based on the output signal from the camangle sensor 92 and executes the ignition (normal pressure ignition).

In step S405, the ECU 70 determines whether or not the crankshaft startsthe rotation by the normal pressure ignition in step S405. Concretely,first, the ECU 70 detects the crank angle after the normal pressureignition, based on the output signal from the crank angle sensor 90 andthe like. By comparing the crank angle thus detected with the crankangle detected in step S403, the ECU 70 determines whether or not thecrank angle is varied to the predetermined angle. Thereby, the ECU 70can determine whether or not the start of the engine 2 succeeds by thefirst explosion (normal pressure ignition) in the stop time expansionstroke cylinder (#1 cylinder). When the crank angle is varied, theprocessing moves to step S409 (step S 406; Yes) On the other hand, whenthe crank angle is not varied, or when the crank angle is not varied tothe predetermined angle even though the crank angle is varied, theprocessing moves to step S407 (step S406; No).

When the processing moves to step S406, the ECU 70 detects the excitingcurrent value of the motor generator 3 via the motor control unit 4.Next, the ECU 70 compares the exciting current value of the motorgenerator 3 detected in step S406 with the predetermined current value.Then, the ECU 70 determines whether or not the exciting current value ofthe motor generator 3 becomes larger than the predetermined currentvalue (step S407). When the exciting current value of the motorgenerator 3 is lager than the predetermined current value, theprocessing moves to step S409 (step S408; Yes).

On the other hand, when the exciting current value of the motorgenerator 3 is smaller than the predetermined current value, theprocessing does not move to step S409 (step S408; No). Namely, thesignificance of the determination in step S408 is to confirm whether ornot the outputting torque of the motor generator 3 becomes enough torotate the crankshaft, by detecting the exciting current value of themotor generator 3 after the energizing thereof. Thereby, it can beprevented that the motor generator is locked as mentioned above.

In step S408, the ECU 70 starts the motoring by the motor generator 3via the motor control unit 4. Thereby, the start of the engine 2 isreliably executed. Next, in step S409, the ECU 70 injects the fuel tothe stop time intake stroke cylinder, and in step S401, the ignition isexecuted to the stop time compression stroke cylinder so that theexplosion occurs, which generates the engine rotation torque. In thatway, the engine starts.

As explained above, the control apparatus of the internal combustionengine of the present invention estimates the cylinder in thecompression stroke and/or the expansion stroke at the time of the enginestop, and supplies the fuel into the cylinder via the intake port whenthe cylinder is in the intake stroke immediately before the engine stop.Thereby, at the time of the engine start, the time until the firstexplosion can be shortened and the engine start can be promptly executedby combusting the fuel introduced and sealed in the cylinder. Since thecranking by the motor is also executed at the same time, getting overthe first and second top dead center becomes easy, while the lock of themotor can be effectively prevented. Thus, the engine start can bereliably executed.

[Modification]

Though the above description is directed to a port injection system,i.e., the case of the engine which executes the fuel injection via aninjector provided in the intake port for convenience of explanation, thepresent invention can also be applied to a cylinder direct injectionsystem, i.e., the engine which executes the fuel injection directly intothe combustion chamber via the injector provided near the top of thepiston head.

INDUSTRIAL APPLICABILITY

The control apparatus of the internal combustion engine according to thepresent invention can be utilized in a vehicle having the internalcombustion engine as power, especially in a field of vehicles havingso-called idling stop functions.

1. A control apparatus of an internal combustion engine comprising: acombustion control unit which controls combustion of the engine at atime of stopping the engine; an inertia energy control unit whichcontrols inertia energy of the engine to be in a predetermined state;and crank angle position by utilizing the inertia energy.
 2. The controlapparatus of the internal combustion engine according to claim 1,wherein the inertia energy control unit controls a number of enginerevolution of the engine to be within a range of a predetermined numberof engine revolution.
 3. The control apparatus of the internalcombustion engine according to claim 2, wherein the inertia energycontrol unit controls the inertia energy by a motor for driving theengine.
 4. The control apparatus of the internal combustion engineaccording to claim 3, wherein the combustion control unit starts thecombustion of the engine while driving by the motor is continued, when astarting request occurs in the engine in a condition that the number ofengine revolution is controlled to be within the predetermined number ofengine revolution by the motor.
 5. The control apparatus of the internalcombustion engine according to claim 1, wherein the stop control unitstops the engine at the predetermined crank angle position by addingcontrol force to the engine by the motor for driving the engine.
 6. Thecontrol apparatus of the internal combustion engine according to claim5, wherein the stop control unit adds the control force to the engine bythe motor for driving the engine when the engine is not estimated tostop at the predetermined crank angle position.
 7. The control apparatusof the internal combustion engine according to claim 5, furthercomprising a detecting unit which detects a number of idling revolutionof the engine, wherein the stop control unit inhibits stopping theengine when the number of idling revolution is larger than apredetermined value.
 8. The control apparatus of the internal combustionengine according to claim 5, further comprising a detecting unit whichdetects the number of idling revolution, wherein the combustion controlunit increases the combustion of the engine to increase the number ofengine revolution before stopping the combustion of the engine when thenumber of idling revolution is smaller than the predetermined value. 9.The control apparatus of the internal combustion engine according toclaim 2, wherein the combustion control unit stops the combustion of theengine when the inertia energy control unit controls the number ofengine revolution to be within the predetermined number of enginerevolution.
 10. The control apparatus of the internal combustion engineaccording to claim 1, further comprising a unit for reducing loads ofthe engine when the stop control unit performs an engine stop control.11. The control apparatus of an internal combustion engine according toclaim 1, further comprising: a start control unit which drives theengine by the motor at a time of engine start; an estimation unit whichestimates a cylinder in a compression stroke and/or an expansion strokeat the time of the engine stop; a detection unit which detects thecylinder; a supplying unit which supplies fuel to the cylinder; and acombustion unit which combusts the fuel supplied to the cylinder at thetime of the engine start.
 12. The control apparatus of the internalcombustion engine according to claim 11, wherein the supplying unitsupplies the fuel to the cylinder via an intake port, or directlysupplies the fuel to the cylinder.
 13. The control apparatus of theinternal combustion engine according to claim 11, wherein thepredetermined crank angle position is a stop position at which a torqueof the motor needed at the time of the engine start becomes small. 14.The control apparatus of the internal combustion engine according toclaim 11, wherein the engine stops at the predetermined crank angleposition by the motor which controls a number of engine revolution to bewithin a predetermined number of engine revolution.
 15. The controlapparatus of the internal combustion engine according to claim 11,wherein the supplying unit supplies the fuel to the cylinder when thecylinder which is detected based on the detection unit immediatelybefore the time of the engine stop is in the intake stroke.
 16. Thecontrol apparatus of the internal combustion engine according to claim11, wherein the start control unit starts the engine by driving themotor when a current value added to the motor is larger than apredetermined value at the time of the engine start.
 17. The controlapparatus of the internal combustion engine according to claim 11,wherein the estimation unit estimates the cylinder which is in thecompression stroke and/or the expansion stroke, based on the number ofengine revolution at a time of stopping driving by the motor.
 18. Thecontrol apparatus of the internal combustion engine according to claim11, wherein the estimation unit estimates the cylinder which is in thecompression stroke and/or the expansion stroke, based on the number ofengine revolution at the time of stopping driving by the motor and akind of the stroke of each cylinder at a time of starting driving by themotor.
 19. The control apparatus of the internal combustion engineaccording to claim 18, wherein the estimation unit specifies the kind ofthe stroke of each cylinder, based on a cam position of the cylinder.